Make the $taxonomy parameter in get_term_field() optional

[DrewAPicture]

Following up on making the $taxonomy parameter in get_term() optional, we should also make it optional in get_term_field().

Patch attached with tests.

[DrewAPicture]

$term should accept an ID or an object

[DrewAPicture]

34245.2.diff​ also makes $term accept both a term ID and WP_Term object, and adds tests. (I really dig being able to use get_term_field() in "shorthand" without having to supply a taxonomy, btw).

[DrewAPicture]

@boonebgorges Might giving this a once over?

Obviously there's a lot of missing tests for get_term_field() just generally, but is there anything I didn't cover for this particular set of changes?

[boonebgorges]

DrewAPicture - This change looks mostly good. Two small suggestions:

1. Since you're modifying the final line of the function anyway, may as well fix the spacing inside the parens :)
2. I'd add a test to show what happens when the value of $taxonomy doesn't match the actual taxonomy of $term. This should be the same before and after the patch - an invalid_term WP_Error object - but the code path is a bit different, in a way that's relevant to the change you're making here.

[DrewAPicture]

@boonebgorges: Addressed your feedback in 34245.3.diff​ and added two tests, one each for the two WP_Error codes that might be returned via get_term().

[boonebgorges]

In 35028:

Don't require a $taxonomy to be specified in get_term_field().

After [34997], the $taxonomy parameter of get_term() is optional. This
changeset brings get_term_field() in line with the new usage.

Adds unit tests for get_term_field().

Props DrewAPicture.
See #34245.

[boonebgorges]

In 35029:

After [35028], normalize get_term_field() doc formatting.

Fixes #34245.