batch (ticdc): add etcdTxnMaxOps to limit the ops number of an etcd txn

[asddongmen]

What problem does this PR solve?

Since #3227 batch multiple changefeed patches into a batch and submit them as an etcd transaction, if there many changefeeds in the cdc cluster, it may cause a "etcdserver: too many operations in txn request\ error.

[2021/11/30 11:32:18.776 +08:00] [INFO] [etcd_worker.go:346] ["changefeed state"] ["changefeed state len"=0] [opsError="json: unsupported type: map[util.EtcdKey][]uint8"]
[2021/11/30 11:32:18.976 +08:00] [INFO] [etcd_worker.go:346] ["changefeed state"] ["changefeed state len"=0] [opsError="json: unsupported type: map[util.EtcdKey][]uint8"]
[2021/11/30 11:32:19.082 +08:00] [INFO] [etcd_worker.go:346] ["changefeed state"] ["changefeed state len"=180] [opsError="json: unsupported type: map[util.EtcdKey][]uint8"]
[2021/11/30 11:32:19.085 +08:00] [INFO] [capture.go:284] ["run owner exited"] [error="etcdserver: too many operations in txn request"] [errorVerbose="etcdserver: too many operations in txn request\ngithub.com/pingcap/errors.AddStack\n\tgithub.com/pingcap/errors@v0.11.5-0.20211009033009-93128226aaa3/errors.go:174\ngithub.com/pingcap/errors.Trace\n\tgithub.com/pingcap/errors@v0.11.5-0.20211009033009-93128226aaa3/juju_adaptor.go:15\ngithub.com/pingcap/ticdc/pkg/orchestrator.(*EtcdWorker).commitChangedState\n\tgithub.com/pingcap/ticdc/pkg/orchestrator/etcd_worker.go:391\ngithub.com/pingcap/ticdc/pkg/orchestrator.(*EtcdWorker).applyPatchGroups\n\tgithub.com/pingcap/ticdc/pkg/orchestrator/etcd_worker.go:333\ngithub.com/pingcap/ticdc/pkg/orchestrator.(*EtcdWorker).Run\n\tgithub.com/pingcap/ticdc/pkg/orchestrator/etcd_worker.go:203\ngithub.com/pingcap/ticdc/cdc/capture.(*Capture).runEtcdWorker\n\tgithub.com/pingcap/ticdc/cdc/capture/capture.go:304\ngithub.com/pingcap/ticdc/cdc/capture.(*Capture).campaignOwner\n\tgithub.com/pingcap/ticdc/cdc/capture/capture.go:282\ngithub.com/pingcap/ticdc/cdc/capture.(*Capture).run.func2\n\tgithub.com/pingcap/ticdc/cdc/capture/capture.go:203\nruntime.goexit\n\truntime/asm_amd64.s:1371"]

What is changed and how it works?

add etcdTxnMaxOps to limit the ops number of an etcd txn

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to update key monitor metrics in both TiCDC document and official document

Release note

Please add a release note.
If you don't think this PR needs a release note then fill it with `None`.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• liuzix
• overvenus

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[overvenus]

LGTM

[overvenus]

Which versions are affected by this issue?

[asddongmen]

Which versions are affected by this issue?

no any for now

[asddongmen]

/run-integration-tests

[liuzix]

/run-integration-tests

[liuzix]

/run-integration-tests

[overvenus]

/merge

[ti-chi-bot]

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

Commit hash: 8610e1f

[asddongmen]

/run-dm-integration-tests

[asddongmen]

This PR needs to cherrypick to release 5.3, 5.2, 5.1, 5.0, 4.0 branch.
I will do this manually.