pkg/orchestrator(ticdc): add timeout before remove capture (#9445)

[ti-chi-bot]

This is an automated cherry-pick of #9445

What problem does this PR solve?

Issue Number: ref #9344

What is changed and how it works?

1. Wait CaptureSessionTTL/2 seconds before removing a capture from GlobalReactorState.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Questions

Will it cause performance regression or break compatibility?

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

Release note

`Fix a bug that could result in double writes after a CDC node disconnects from etcd.`.

[ti-chi-bot]

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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	55551f7	link	true	/test verify
pull-dm-integration-test	55551f7	link	true	/test dm-integration-test
pull-cdc-integration-mysql-test	55551f7	link	true	/test cdc-integration-mysql-test
pull-cdc-integration-kafka-test	55551f7	link	true	/test cdc-integration-kafka-test
pull-dm-compatibility-test	55551f7	link	true	/test dm-compatibility-test

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