Rehome 21 tests/ui/issues/ tests to other subdirectories under tests/ui/

[Oneirical]

#143902 divided into smaller, easier to review chunks.

Part of #133895

Methodology:

1. Refer to the previously written tests/ui/SUMMARY.md
2. Find an appropriate category for the test, using the original issue thread and the test contents.
3. Add the issue URL at the bottom (not at the top, as that would mess up stderr line numbers)
4. Rename the tests to make their purpose clearer

Inspired by the methodology that @Kivooeo was using.

r? @jieyouxu

[rustbot]

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[rustbot]

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

[jieyouxu]

For future PRs like this where you have both moves and edits, can you make sure to split the changes into two commits, with commit 1 being move-only, and commit 2 being edits? This is intended to make it easier to navigate git history. I wouldn't worry so much about PRs you already have opened.