snapshot(ticdc): fix ddl puller and ddl manager stuck caused by dead lock (#11886)

[ti-chi-bot]

This is an automated cherry-pick of #11886

What problem does this PR solve?

Issue Number: close #11884

What is changed and how it works?

Summary

This PR fixes a deadlock issue in the Snapshot implementation:

Deadlock in Recursive Read Locking: Although Go’s sync.RWMutex allows recursive read locks, they can result in deadlocks if a write lock is requested during the recursive read lock execution. This blocks the outer read lock from releasing, preventing the write lock from proceeding.

This PR refactors lock usage patterns to avoid recursive read locking.

---

Root Causes of the Deadlocks

Recursive Read Lock Issue

Recursive calls involving RWMutex.RLock() can result in deadlocks when a write lock is requested during the recursive read lock execution. This behavior arises because Go’s sync.RWMutex prioritizes write locks over read locks.

Here is an example that illustrates the problem:

func (s *Snapshot) Operation() {
    s.rwlock.RLock()
    defer s.rwlock.RUnlock()
    s.NestedOperation() // Second RLock
}

func (s *Snapshot) NestedOperation() {
    s.rwlock.RLock()
    defer s.rwlock.RUnlock()
    // Perform some operations
}

If a write lock is requested while NestedOperation is executing, the following chain of events occurs:

1. The write lock request blocks new readers, including the recursive RLock in NestedOperation.
2. NestedOperation cannot complete until its RLock is granted.
3. The first RLock in Operation cannot release until NestedOperation completes.
4. Deadlock occurs because the first RLock and the recursive RLock are mutually dependent.

Check List

Tests

• Unit test
• Integration test

Questions

Will it cause performance regression or break compatibility?

No.

Do you need to update user documentation, design documentation or monitoring documentation?

No.

Release note

None.

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[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
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[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
jenkins-ticdc/verify	d41c731	link	true	/test verify
pull-cdc-integration-mysql-test	d41c731	link	true	/test cdc-integration-mysql-test
pull-cdc-integration-kafka-test	d41c731	link	true	/test cdc-integration-kafka-test
pull-cdc-integration-storage-test	d41c731	link	true	/test cdc-integration-storage-test

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