branch-4.1: [opt](file-cache) support config hot reload of file cache microbench in running state

[gavinchou]

Summary

Pick #58922 to branch-4.1

Changes

• Add reload_file_cache method to FileCacheFactory for hot reloading file cache configuration
• Add RELOAD operation to FileCacheAction HTTP endpoint
• Refactor file_cache_microbench to support config hot reload in running state
  • Introduce BenchEnvManager class to manage config loading and reload worker
  • Add reload_config and show_reload_status RPC endpoints
  • Improve read buffer management in JobManager

Related Issue

close #58922

[Thearas]

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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[gavinchou]

run buildall