*: provide a option to wait for init stats to finish before providing service during startup (#43381)

[ti-chi-bot]

This is an automated cherry-pick of #43381

What problem does this PR solve?

Issue Number: close #43385 ref #42160

Problem Summary:

What is changed and how it works?

Introduce the configuration force-init-stats, which indicates whether to wait for init stats to finish before providing service during startup.

Check List

Tests

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

Add time.Sleep(30 * time.Second) at the beginning of init stats to simulate slow init stats. Start the tidb node with setting force-init-stats to true. The connection from mysql client is accepted after init stats is finished(after roughly 30 sec).

• 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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[ti-chi-bot]

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[winoros]

won't go to 5.0