Internal Version 2021.05.12.1

Release v2021.05.12.1 (#921)

* fix(ttlcache): goroutine leak (#892)
* tidb: forwarder only uses tidb whose status is Up (#893)
* keyviz: Add tips for enabled config (#901)
* ui: rocksdb fields (#896)
* monitoring: setup sentry (#895)
* tidb_client: improve behavior when no alive tidb instance (#900)
* feat(stmt): support config maximum number of stmt kept in memory (#914)
* feat: debug api (#898)
* ui: Improve settings description for Statement (#920)
* feat(ui): add tiflash profiling option (#859)
* ui: Add a warning for the debug API (#922)