Similar to other function in the `_deprecated_*` series, `_deprecated_class()` comes with two new hooks: `deprecated_class_run` and `deprecated_class_trigger_error`.
Support has also been added for setting class deprecation expectations in tests.
Props jrf, wvega, ohryan.
See #41125.
git-svn-id: https://develop.svn.wordpress.org/trunk@56467 602fd350-edb4-49c9-b593-d223f7449a82