owner: fix owner doesn't clean up stale tasks (#1163)

[ti-srebot]

cherry-pick #1163 to release-4.0

---

What problem does this PR solve?

Fix https://github.com/pingcap/ticdc/issues/1158

• TiCDC should clean the metadata of a changefeed as thoroughly as possible when removing a changefeed, but it is still possible to leave redundant metadata.
• Owner should choose whether to filter metadata when using it or clean up redundant data regularly, this PR chooses the second way.

What is changed and how it works?

Owner clean up the stale tasks at the beginning of each run round.

Check List

Tests

• Unit test
• Integration test

Release note

• Fix a bug that outdated metadata could cause the newly created changefeed abnormal.

[ti-srebot]

/run-all-tests

[overvenus]

LGTM

[codecov-io]

Codecov Report

Merging #1184 (28bdf31) into release-4.0 (ba68bc1) will increase coverage by 0.2059%.
The diff coverage is 30.7692%.

@@                 Coverage Diff                 @@
##           release-4.0      #1184        +/-   ##
===================================================
+ Coverage      39.8383%   40.0442%   +0.2059%     
===================================================
  Files              112        112                
  Lines            11750      11752         +2     
===================================================
+ Hits              4681       4706        +25     
+ Misses            6597       6566        -31     
- Partials           472        480         +8     

[liuzix]

LGTM

[amyangfei]

/merge

[ti-srebot]

Your auto merge job has been accepted, waiting for:

• 1142

[ti-srebot]

/run-all-tests

[ti-srebot]

@ti-srebot merge failed.

[amyangfei]

/merge

[ti-srebot]

/run-all-tests