ddl: decouple job scheduler from 'ddl' and make it run/exit as owner changes (#53548)

[ti-chi-bot]

This is an automated cherry-pick of #53548

What problem does this PR solve?

Issue Number: ref #53246

Problem Summary:

What changed and how does it work?

• decouple ddl job scheduler part out of ddl partially, some fields are still coupled, and make it a separate and cancellable module. it should make further test easier.
  • all context usage now changed to scheduler/worker context which is only valid during being owner from ddl context
  • current ddl context is non-cancellable, which might cause some issue when owner change, as it cannot be cancelled in time, it might keeps running until we hopefully met some isOwner check, so the duration of co-exist of 2 owner might be quite long.
• after this pr, job scheduler related routine will only be start when current node is elected as owner. start SyncJobSchemaVerLoop only on owner node.
• fix add-index disttask scheduler uses the 'ddlCtx.ctx', it should use the context we pass in.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  • tiup a cluster with 3 tidb
  • run a script to create 1000 tables with 10 threads, during this time we keeps delete keys of prefix /tidb/ddl/fg/owner/, to force owner change
  • ddl should be run success, and no abnormal output in logs.

mysql> select count(1) from INFORMATION_SCHEMA.tables where table_schema='ff_0';
+----------+
| count(1) |
+----------+
|     1000 |
+----------+
1 row in set (0.01 sec)

• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

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