* Synchronization has been added to `LoggerSilence#silence`.
* Fix #10856: search pending migrations among all known migrations, not
only the latest one. `ActiveRecord::Migrator.needs_migration?` works
as expected now.
* Fix #10789: `LoggerSilence` included into `::Logger`.
* Revert 3970432fcb6a0: it is very bad idea to use mtime to check if
there are pending migrations. Suppose you did `db:migrate/db:rollback`
several times: checking will stop work at all (`db:migrate:status` has
changed but mtime is not).