So everything can be loaded using PSR-4. These classes weren't renamed,
nor the alias for the AbuseFilter class was deprecated, because they
should be refactored first.
Change-Id: Ia328db58eb326968edf5591daac9bacf8c2f75da
$wgAbuseFilterActions shouldn't be used normally, as it excludes actions
registered by other extensions.
Note: mw:Extension:AbuseFilter#Integration_with_other_extensions should
be updated after merging.
Bug: T239348
Change-Id: I89b3f0228eacdf145e8f2dd2a5602d0c7ce75a86