meta/autoid: enable etcd client auto sync for autoid service (#43529)

[ti-chi-bot]

This is an automated cherry-pick of #43529

What problem does this PR solve?

Issue Number: close #42643

ref #9575, ref #33908

Problem Summary:

When the pd server change, the corresponding etcd address should be auto-refresh on the client side.

What is changed and how it works?

While it is easy to just add back the option AutoSyncInterval: 30 * time.Second in, I think a bigger issue is why do we need to have 4 different etcd clients rather than sharing the same one with all the correct config 🤷

Because 1. tidb repo is too big, and it's not designed to be used as a lib. (this applies to all tidb/util/xxx), so the etcd client utility in the tidb repo is not a good place to be shared by other repos (tools / binlog ...)
2. For autoid service, it's a indenpendent component, the code is put to the tidb repo though. So this case is similiar to tools etc.
It should have shared the same etcd client instance, but it's not available when the server startup.

Maybe we can maintain a pingcap/etcdutil lib to solve the " 4 different etcd clients" issue

Check List

Tests

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

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

[ti-chi-bot]

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• hawkingrei

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idc-jenkins-ci-tidb/unit-test	683f3b1	link	true	/test unit-test

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This pull-request has been approved by: hawkingrei

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[tiancaiamao]

No need to cherry-pick #43529 to 7.1
Because #38975 contains the fix on 7.1

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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