WP_Term_Query should support querying by `term_taxonomy_id`

[boonebgorges]

Breaking off from #37038 and other places where this has been mentioned.

get_terms() and WP_Term_Query support querying by 'name' and 'slug', but not 'term_taxonomy_id'. Let's fix this.

[boonebgorges]

In 37682:

Tests: Move WP_Tax_Query tests to a more appropriate file.

The file they were living in is the rightful home of WP_Term_Query tests.

See #37074.

[boonebgorges]

In 37683:

Introduce term_taxonomy_id parameter for WP_Term_Query.

Allows the fetching of terms based on term_taxonomy_id, or an array of
term_taxonomy_ids.

Props spacedmonkey.
Fixes #37074.