*: refactor Allocator.Alloc() interface for separating auto IDs

[tangenta]

What problem does this PR solve?

The first step to solve the issue: #982.

What is changed and how it works?

This PR moves the table ID argument from Alloc() to the initializing stage. There is at least one allocator for each table, so the change is reasonable.

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AilinKid
• wjhuang2016

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[tangenta]

/merge

[ti-chi-bot]

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

Commit hash: e5aa751

[ti-chi-bot]

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