Related to KT-56623, KT-56587 #KT-59344 Fixed
* Also, mention implementation details of EnumEntries to enable safe uses of a 'EnumEntries' as a set * Fix testdata for opt-in marker in enum entries ^KT-58548 fixed Merge-request: KT-MR-10037 Merged-by: Vsevolod Tolstopyatov <qwwdfsad@gmail.com>
^KT-53153