kv-client: fix stream is not recycled when meeting recv error (#1336)

[ti-srebot]

cherry-pick #1336 to release-4.0
You can switch your code base to this Pull Request by using git-extras:

# In ticdc repo:
git pr https://github.com/pingcap/ticdc/pull/1373

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/ticdc.git pr/1373:release-4.0-96fb4549fff4

---

What problem does this PR solve?

• Find a but that gRPC stream is not recycled correctly in some scenarios
  • if stream.Recv with error, but the underlying stream is normal actually (or the next round of stream.Send is successfully, then the receiveFromStream goroutine will be never created, and corresponding events will not be consumed by kv client.
• Improve unit test of kv client, part of Improve unit tests of kv client #1292

What is changed and how it works?

• Close stream before receiveFromStream routine exits, and remove stream from stream cache
• Add unit test to cover this scenario

Check List

Tests

• Unit test
• Integration test

Release note

• Fix a bug that kv client may skip to recreate event feed receiving routine by accident.

[ti-srebot]

/run-all-tests

[amyangfei]

/merge

[ti-srebot]

Your auto merge job has been accepted, waiting for:

• 1370

[ti-srebot]

/run-all-tests