Release 1.6.4

[RidRisR]

This is an issue tracking the tidb-operator v1.6.4 release.

• Release 1.6.3 #6302

TODO:

• Update default version of TiDB Operator bump TiDB Operator to 1.6.4 #6501

• Update TiDB version and tools version if necessary

• Update the tools version in docs-tidb-operator repo bump TiDB Operator to 1.6.4 #6501

• Update release notes Release doc for 1.6.4 docs-tidb-operator#2954

• Update Github Releases

• Build and publish docker images/helm charts

• Announcement (email, etc.)

• Update TiDB Operator version in docs-tidb-operator repo (both for dev and stable branch) Release doc for 1.6.4 docs-tidb-operator#2954