This was removed in [29915] as part of the attempt to add cache support to
`get_term_by()`. When that support was removed in [30900], it was not properly
restored.
This changeset includes a unit test to verify that the cache is properly primed
for terms found in `get_terms()`, as well as tests to verify the other cache
setting that was touched by [30900].
Fixes#30749. See #21760.
git-svn-id: https://develop.svn.wordpress.org/trunk@30954 602fd350-edb4-49c9-b593-d223f7449a82