refactor AttributeGate and rustc_attr! to emit notes during feature checking

[mejrs]

This PR changes the following:

• AttributeGate from an enum with (four) tuple fields to (five) named fields
• adds a notes fields that is emitted as notes in the PostExpansionVisitor pass
• removes the this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date note if the feature gate is rustc_attrs.
• various phrasing changes and touchups
• and finally, the reason why I went down this path to begin with: tell people they can use the diagnostic namespace when they hit the rustc_on_unimplemented feature gate 🙈

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[mejrs]

It looks like this code had some shadowing issues causing name to refer to the feature gate name, not the attribute. So I've changed it, but note that I think this function is dead code.

[rust-log-analyzer]

The job mingw-check-tidy failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

info: removing rustup binaries
info: rustup is uninstalled
##[group]Image checksum input
mingw-check-tidy
# We use the ghcr base image because ghcr doesn't have a rate limit
# and the mingw-check-tidy job doesn't cache docker images in CI.
FROM ghcr.io/rust-lang/ubuntu:22.04

ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get install -y --no-install-recommends \
  g++ \
---

COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
COPY host-x86_64/mingw-check/validate-error-codes.sh /scripts/

# NOTE: intentionally uses python2 for x.py so we can test it still works.
# validate-toolstate only runs in our CI, so it's ok for it to only support python3.
ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test \
           --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
#
# This file is autogenerated by pip-compile with Python 3.10
# by the following command:
#
#    pip-compile --allow-unsafe --generate-hashes reuse-requirements.in
---
#12 2.983 Building wheels for collected packages: reuse
#12 2.984   Building wheel for reuse (pyproject.toml): started
#12 3.195   Building wheel for reuse (pyproject.toml): finished with status 'done'
#12 3.196   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132719 sha256=d2a2565e7037ad3883fb9337653f2e25bbb588534fbef3697286cbc26d1bf634
#12 3.197   Stored in directory: /tmp/pip-ephem-wheel-cache-xebn3k3c/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#12 3.199 Successfully built reuse
#12 3.199 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#12 3.588 Successfully installed attrs-23.2.0 binaryornot-0.4.4 boolean-py-4.0 chardet-5.2.0 jinja2-3.1.4 license-expression-30.3.0 markupsafe-2.1.5 python-debian-0.1.49 reuse-4.0.3 tomlkit-0.13.0
#12 3.589 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#12 4.127 Collecting virtualenv
#12 4.164   Downloading virtualenv-20.31.2-py3-none-any.whl (6.1 MB)
#12 4.234      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 6.1/6.1 MB 89.7 MB/s eta 0:00:00
#12 4.292 Collecting platformdirs<5,>=3.9.1
#12 4.295   Downloading platformdirs-4.3.8-py3-none-any.whl (18 kB)
#12 4.333 Collecting filelock<4,>=3.12.2
#12 4.336   Downloading filelock-3.18.0-py3-none-any.whl (16 kB)
#12 4.355 Collecting distlib<1,>=0.3.7
#12 4.358   Downloading distlib-0.3.9-py2.py3-none-any.whl (468 kB)
#12 4.366      ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 469.0/469.0 KB 85.0 MB/s eta 0:00:00
#12 4.447 Installing collected packages: distlib, platformdirs, filelock, virtualenv
#12 4.636 Successfully installed distlib-0.3.9 filelock-3.18.0 platformdirs-4.3.8 virtualenv-20.31.2
#12 4.637 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#12 DONE 4.7s

#13 [7/8] COPY host-x86_64/mingw-check/validate-toolstate.sh /scripts/
#13 DONE 0.0s
---
DirectMap4k:      128960 kB
DirectMap2M:     7211008 kB
DirectMap1G:    11534336 kB
##[endgroup]
Executing TIDY_PRINT_DIFF=1 python2.7 ../x.py test            --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
+ TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 src/tools/tidy tidyselftest --extra-checks=py,cpp
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.05s
##[endgroup]
WARN: currently no CI rustc builds have rustc debug assertions enabled. Please either set `rust.debug-assertions` to `false` if you want to use download CI rustc or set `rust.download-rustc` to `false`.
downloading https://static.rust-lang.org/dist/2025-05-12/rustfmt-nightly-x86_64-unknown-linux-gnu.tar.xz
---
fmt check
fmt: checked 6017 files
tidy check
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:744: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:748: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:752: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:756: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:760: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:802: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:816: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:826: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:853: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:864: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:870: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:876: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:882: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:888: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:894: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:900: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:912: trailing whitespace
##[error]tidy error: /checkout/compiler/rustc_feature/src/builtin_attrs.rs:961: trailing whitespace
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'venv'
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'virtualenv'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (25.1.1)
linting python files
All checks passed!
checking python file formatting
26 files already formatted
checking C++ file formatting
some tidy checks failed
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:01:48
  local time: Sat May 17 23:43:12 UTC 2025
  network time: Sat, 17 May 2025 23:43:12 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[workingjubilee]

cc @jdonszelmann

[jdonszelmann]

I'll take a look