Fix #3010 - middleware error on invalid keywords

[yuhan0]

Fixes #3010 - cider-tooling-eval does not throw middleware errors if the keyword is invalid.

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If you're just starting out to hack on CIDER you might find this section of its
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[bbatsov]

The change seems reasonable, but it's breaking the tests.

[yuhan0]

I think this should work now.. but it's quite ugly to be requiring all these external repl-related functions from a util namespace.

I originally made this change to better support cider-browse-spec on the common use of auto namespaced ::keyword specs - perhaps the logic should belong there instead.

[yuhan0]

Added commits which revert all the changes to cider-symbol-at-point and move the :: expansion logic to cider-browse-spec (which doesn't have tests), let me know which you prefer and I'll squash the relevant commits

[bbatsov]

@yuhan0 I like the second solution better, so let's go with it.

[bbatsov]

Thanks!