Add some unit tests for `is_object_in_term()`.

These tests check a number of the ways that different kinds of values for
`$terms` (integers that match term_id, strings that match term_id or name or
slug) are handled.

See #29467.
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git-svn-id: http://core.svn.wordpress.org/trunk@30204 1a063a9b-81f0-0310-95a4-ce76da25c4cd
In `in_object_in_term()`, only check numeric string values against term_id.

The previous `in_array()` check was playing too loose with mixed types, such
that a string like '10_term_name' would incorrectly match a term_id 10.

Props nobinobi, realloc.
Fixes #29467.
Built from https://develop.svn.wordpress.org/trunk@30205


git-svn-id: http://core.svn.wordpress.org/trunk@30205 1a063a9b-81f0-0310-95a4-ce76da25c4cd