Organize phpunit tests by component (better)

[DrewAPicture]

In working to improve our contributor documentation in the core contributor handbook, part of that is to make organization of the core unit tests be a more predictable.

A great deal of our tests are already organized by component, that is to say comment-template => comment/template.php, post-template.php => post/template.php, etc.

However, there are still quite a few tests scattered all over the place in multiple files. This will serve as a tracking ticket for relocating those wayward tests.

[DrewAPicture]

In 34687:

Tests: Consolidate author-template tests into a single, more logically-placed file, tests/user/author.php.

See #34070.

[DrewAPicture]

In 34688:

Tests: Relocate tests for general-template.php to a more logically-placed (and named) file, tests/general/template.php.

See #34070.