EtcdWorker: fix EtcdWorker snapshot isolation (#2510)

[ti-chi-bot]

This is an automated cherry-pick of #2510

What problem does this PR solve?

• EtcdWorker's snapshot isolation is violated if there are two concurrent transactions one deleting and the other putting to the same key.
• EtcdWorker's snapshot isolation is violated if while A is running and trying to create a key k, B and C creates and deletes k sequentially.

What is changed and how it works?

• For the first case, we use equality of mod_revision to check for write-set intersection instead of inequality.
• For the second case, we use a global deleteCounter as a key to make deletions impossible to race with other operations.

Check List

Tests

• Unit test
• Integration test

Code changes

• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity

Related changes

• Need to cherry-pick to the release branch

Release note

Fix a bug in metadata management

[ti-chi-bot]

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[amyangfei]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 5715964

[amyangfei]

/run-integration-tests
/run-kafka-tests

[amyangfei]

/run-kafka-tests