ddl: Support parsing VectorIndex defined in IndexInfo

[Lloyd-Pottiger]

What problem does this PR solve?

Issue Number: ref #9032

Problem Summary:

What is changed and how it works?

• Support parsing VectorIndex defined in IndexInfo
• Use constant TiDB::MAX_VECTOR_DIMENSION to replace magic number in codes
• Fix a fake lock safe func FileCache::fgDownload

ddl: Support parsing VectorIndex defined in IndexInfo

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

[zimulala]

LGTM

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JaySon-Huang, zanmato1984, zimulala

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-20 09:31:05.242316137 +0000 UTC m=+1212734.982740073: ☑️ agreed by JaySon-Huang.
• 2024-09-20 09:54:10.16647876 +0000 UTC m=+1214119.906902696: ☑️ agreed by zanmato1984.