Bulgarian translation by Ivan Cenov (#15369).
Fixed UI tests.
Use :button_edit instead of :button_update for editing issues (#15275).
Use :button_save instead of :button_update on committers form (#15275).
Removed deferred tests.
Merged r12265, r12268, r12272 (#15307).
Merged r12278 (#15311).
Merged r12277 (#15344).