Release v1.3.8

[KanShiori]

This is an issue tracking the tidb-operator v1.3.4 release.

Previous:

• release 1.1.0 #2567
• release v1.1.1 #2775
• release v1.1.2 #2839
• release v1.1.3 #3010
• Release v1.1.4 #3140
• Release v1.1.5 #3263
• Release v1.1.6 #3380
• Release v1.1.7 #3495
• Release v1.1.8 #3616
• Release v1.1.9 #3656
• Release v1.1.10 #3754
• Release v1.1.11 #3812
• Release v1.1.12 #3919
• Release v1.1.13 #4049
• Release v1.1.14 #4231
• Release v1.2.0-beta.2 #3950
• Release v1.2.0-rc.1 #3998
• Release v1.2.0-rc.2 #4055
• Release v1.2.0 #4104
• Release v1.2.1 #4142
• Release v1.2.2 #4174
• Release v1.2.3 #4182
• Release v1.2.4 #4230
• Release v1.2.5 #4329
• Release v1.2.6 #4339
• Release v1.3.0-beta.1 #4365
• Release v1.3.0 #4409
• Release v1.3.1 #4432
• release v1.3.2 #4476
• Release v1.3.3 #4523
• Release v1.3.4 #4553
• Release v1.3.5 #4568
• Release v1.3.7 #4657
• Release v1.3.8 #4699

Pending PRs:

TODO:

• Update default version of TiDB Operator bump operator to v1.3.8 #4701
• Update TiDB version and tools (may include DM) version if necessary
• Update TiDB version and tools in the docs-tidb-operator repo if necessary
• Update release notes en,zh: release notes for 1.3.8 docs-tidb-operator#1995
• Update Github Releases
• Build and publish docker images/helm charts
• Announcement (slack, email, etc.)
• Update TiDB Operator version in docs-tidb-operator repo bump operator to v1.3.8 docs-tidb-operator#1992