Revert "Try enabling -Wsuggest-override again, using add_compile_options instead of add_compile_definitions for disabling it in unittests/ directories."

This reverts commit 388c9fb1af48b059d8b65cb2e002e0992d147aa5.

GitOrigin-RevId: 97a0f80c469c338e9173355e9f8a0a977adfe266