Add integration test for tool removal during platform uninstall

Tool dependency by `arduino-cli core uninstall` is somewhat complex because it must only uninstall the tools that no
other platforms have a dependency on. If it doesn't, it breaks the other platform and the cause of this breakage would
likely not be obvious to the user.

So it's important to test to ensure this functionality continues to work correctly.

Author: per1234

test/test_core.py

@@ -205,6 +205,49 @@ def test_core_uninstall(run_command):
     assert not _in(result.stdout, "arduino:avr")
 
 
+def test_core_uninstall_tool_dependency_removal(run_command):
+    # These platforms both have a dependency on the arduino:[email protected] tool
+    # arduino:[email protected] has a dependency on arduino:[email protected]
+    assert run_command("core install arduino:[email protected]")
+    # arduino:[email protected] has a dependency on arduino:[email protected]
+    assert run_command("core install arduino:[email protected]")
+    assert run_command("core uninstall arduino:avr")
+
+    result = run_command("config dump --format json")
+    assert result.ok
+    settings_json = json.loads(result.stdout)
+    arduino_tools_path = os.path.join(
+        settings_json["directories"]["data"],
+        "packages",
+        "arduino",
+        "tools"
+    )
+
+    avr_gcc_binaries_path = os.path.join(
+        arduino_tools_path,
+        "avr-gcc",
+        "7.3.0-atmel3.6.1-arduino5",
+        "bin"
+    )
+    # The tool arduino:[email protected] that is a dep of another installed platform should remain
+    assert (
+        os.path.exists(os.path.join(avr_gcc_binaries_path, "avr-gcc"))
+        or os.path.exists(os.path.join(avr_gcc_binaries_path, "avr-gcc.exe"))
+    )
+
+    avrdude_binaries_path = os.path.join(
+        arduino_tools_path,
+        "avrdude",
+        "6.3.0-arduino17",
+        "bin"
+    )
+    # The tool arduino:[email protected] that is only a dep of arduino:avr should have been removed
+    assert (
+        os.path.exists(os.path.join(avrdude_binaries_path, "avrdude"))
+        or os.path.exists(os.path.join(avrdude_binaries_path, "avrdude.exe"))
+    ) is False
+
+
 def test_core_zipslip(run_command):
     url = "https://raw.githubusercontent.com/arduino/arduino-cli/master/test/testdata/test_index.json"
     assert run_command("core update-index --additional-urls={}".format(url))