Move ui/issues tests to relevant subdirectories

[kyleecodes]

Related to #133895 and Reorganisation of tests/ui/issues for GSOC

This is the first PR in a batch of PRs.

Moves ui/issues/issue-17546.rs‎ ‎-> ui/variants/variant-result-noresult-used-as-type.rs

Approach:

1. Check linked issue and test contents, determine new target directory
2. Move / rename tests to reflect purpose.
3. Add issue link / comments in separate commit.
4. Rebless if necessary and remove obsolete stderr.

r? @Kivooeo

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r? @jieyouxu

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[kyleecodes]

Marked draft to modify the target directory.

Also, I'll keep all commit msgs the same format moving forward. Happy to fix that here if needed.

[zedddie]

Hey! you don't need to bless in the first (move) commit, since you'll rebless anyway after adding metadata in the next one (and the move commit should only consist of moves.) . It makes less noise in the diff if you just move first, then bless + add metadata together.

[kyleecodes]

Makes sense, with issue links updating stderr line numbers. I'll update my approach to separate the move, then commit rebless with metadata / code changes.