Fixes `WP_List_table` tests leaking into other tests by:
* Restores the original `$hook_suffix` global value.
Rather than modifying the global for all tests, it now restores the original value between tests. Why? To ensure each test starts at a known state.
* Uses a new instance of `WP_List_Table` for each test.
A test may modify the `$list_table` object. If it does, it could impact tests yet to run. By instantiating a new instance in the `set_up()` test fixture, each test is isolated from the others.
Follow-up to [53868], [54215].
Props hellofromTonya, antonvlasenko.
See #58955, #58896.
git-svn-id: https://develop.svn.wordpress.org/trunk@56348 602fd350-edb4-49c9-b593-d223f7449a82
88570fd5b3