sink/mysql: rollback txn to recycle db conn, refine timeout param in db conn (#1279)

[ti-srebot]

cherry-pick #1279 to release-5.0-rc

What problem does this PR solve?

Fix bug in #1261 & #1275

What is changed and how it works?

• Rollback txn if txn execute with failure, to fix mysql sink is blocked by mysql client #1275
• Add readTimeout/writeTimeout/timeout parameter in all MySQL dsns to fix Creating sink blocks owner #1261
• Fix another bug that resource is not cleared if get db connection with error
• Add unit test cases to verify the three bug fixes.

Besides, this PR doesn't introduce any timeout context to control database operation, since at current stage, TiCDC doesn't need to have an accurate running time limit for database operation.

Check List

Tests

• Unit test
• Integration test

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
  • add read-timeout, write-timeout and timeout in sink uri parameters

Release note

• Fix a bug that MySQL connection is not recycled when some transactions executed with failure.
• Fix a bug that MySQL sink could hang if downstream TiDB/MySQL is not available.

[amyangfei]

/run-all-tests

[liuzix]

LGTM

[amyangfei]

/merge

[ti-srebot]

/run-all-tests