[Store]: Refactor AllocationStrategy implementation for better performance and flexibility

[nickyc975]

Description

This PR refactored the AllocationStrategy implementation according to the RFC #1131 . Unit tests and documentations are also updated accordingly.

Type of Change

• Types
  • [ ] Bug fix
  • [ ] New feature
    • [ ] Transfer Engine
    • [ ] Mooncake Store
    • [ ] Mooncake EP
    • [ ] Integration
    • [ ] P2P Store
    • [ ] Python Wheel
  • [ ] Breaking change
  • [ ] CI/CD
  • [ ] Documentation update
  • [x] Other
    • [x] Performance optimization

How Has This Been Tested?

• Existing unit tests have been updated according to the new interface, and all of them are passed.
• 5 new unit test cases are added to test the new functionalities, and all of them are passed.
• A new preformance test case is added to validate the performance improvement, and here is the result:

Before optimization:

# Round 0
Allocation Strategy Performance Test:
Num segments: 512
Num allocations: 5000
Time elapsed: 8120.33 us

# Round 1
Allocation Strategy Performance Test:
Num segments: 512
Num allocations: 5000
Time elapsed: 8177.32 us

# Round 2
Allocation Strategy Performance Test:
Num segments: 512
Num allocations: 5000
Time elapsed: 8151.01 us

After the optimization:

# Round 0
Allocation Strategy Performance Test:
Num segments: 512
Num allocations: 5000
Time elapsed: 3140.84 us

# Round 1
Allocation Strategy Performance Test:
Num segments: 512
Num allocations: 5000
Time elapsed: 3217.19 us

# Round 2
Allocation Strategy Performance Test:
Num segments: 512
Num allocations: 5000
Time elapsed: 3140.77 us

Checklist

• [x] I have performed a self-review of my own code.
• [x] I have updated the documentation.
• [x] I have added tests to prove my changes are effective.

[gemini-code-assist[bot]]

Summary of Changes

Hello @nickyc975, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly overhauls the core buffer allocation mechanism within the Mooncake Store. By introducing a dedicated manager for allocators and refining the allocation strategy's interface, the changes aim to provide a more robust, flexible, and performant system for managing storage resources. The refactoring streamlines how buffer allocations are requested and processed, allowing for better control over where data replicas are placed and leading to a notable boost in allocation speed.

Highlights

• Refactored AllocationStrategy: The AllocationStrategy implementation has been refactored according to RFC #1131, enhancing both performance and flexibility in buffer allocation.
• Introduced AllocatorManager: A new AllocatorManager class has been introduced to centralize the management of buffer allocators, simplifying the AllocationStrategy interface and improving organization.
• Enhanced Allocation Parameters: The Allocate method now accepts replica_num, preferred_segments, and excluded_segments as parameters, providing more granular control over allocation preferences.
• Significant Performance Improvement: Performance tests demonstrate a substantial speedup in allocation, reducing elapsed time for 5000 allocations from approximately 8ms to 3ms.
• Updated Documentation and Tests: All relevant unit tests and documentation (English and Chinese) have been updated to reflect the new interface and functionalities, with new test cases added for the enhanced features.

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