Implement adaptive buffer sizing with workload profiles - Production-Ready Implementation (#878)

* Initial plan

* Add workload profiles module with adaptive buffer sizing

Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

* Add comprehensive adaptive buffer sizing documentation

Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

* Add implementation summary documentation

Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

* Implement Phase 2: Opt-In Usage for buffer profiles

- Add RUSTFS_BUFFER_PROFILE_ENABLE and RUSTFS_BUFFER_PROFILE config options
- Implement global buffer configuration with enable/disable flag
- Add WorkloadProfile::from_name() for parsing profile names
- Update put_object, put_object_extract, and upload_part to use opt-in function
- Add init_buffer_profile_system() in main.rs for initialization
- Add comprehensive tests for opt-in functionality
- Update documentation with Phase 2 usage examples

Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

* Implement Phase 3: Default Enablement for buffer profiles

- Change default to enabled with GeneralPurpose profile
- Replace --buffer-profile-enable with --buffer-profile-disable for opt-out
- Update init_buffer_profile_system() to reflect Phase 3 logic
- Add comprehensive Phase 3 documentation
- Create MIGRATION_PHASE3.md guide for smooth transition
- Add test for Phase 3 default behavior
- Update IMPLEMENTATION_SUMMARY.md to mark Phase 3 as complete

Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

* Implement Phase 4: Full Integration with deprecated legacy and metrics

- Deprecate get_adaptive_buffer_size() function (backward compatible)
- Implement profile-only buffer sizing in get_buffer_size_opt_in()
- Add performance metrics collection (optional, via metrics feature)
- Even disabled mode now uses GeneralPurpose profile (no hardcoded values)
- Add comprehensive Phase 4 documentation and guide
- Add test_phase4_full_integration() test
- Update IMPLEMENTATION_SUMMARY.md to mark Phase 4 as complete

Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

* Finalize adaptive buffer sizing: remove deprecated code and improve documentation

English:
- Remove deprecated get_adaptive_buffer_size() function
- Remove deprecated test cases (test_adaptive_buffer_size, Phase 3 legacy comparisons)
- Improve all code comments to be clear and professional English
- Add comprehensive bilingual implementation summary (COMPLETE_SUMMARY.md)
- Update buffer sizing comments in put_object, put_object_extract, upload_part
- Enhance init_buffer_profile_system documentation
- Clean up phase-specific references in comments

Chinese (中文):
- 移除已弃用的 get_adaptive_buffer_size() 函数
- 移除已弃用的测试用例（test_adaptive_buffer_size、Phase 3 旧版比较）
- 改进所有代码注释，使用清晰专业的英文
- 添加全面的双语实现摘要（COMPLETE_SUMMARY.md）
- 更新 put_object、put_object_extract、upload_part 中的缓冲区调整注释
- 增强 init_buffer_profile_system 文档
- 清理注释中的特定阶段引用

This commit completes the adaptive buffer sizing implementation by:
1. Removing all deprecated legacy code and tests
2. Improving code documentation quality
3. Providing comprehensive bilingual summary

本提交完成自适应缓冲区大小实现：
1. 移除所有已弃用的旧代码和测试
2. 提高代码文档质量
3. 提供全面的双语摘要

Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>

* fmt

* fix

* fix

* fix

* fix

---------

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Co-authored-by: houseme <4829346+houseme@users.noreply.github.com>
Co-authored-by: houseme <housemecn@gmail.com>

rustfs/Cargo.toml

@@ -31,7 +31,8 @@ name = "rustfs"
 path = "src/main.rs"
 
 [features]
-default = []
+default = ["metrics"]
+metrics = []
 
 [lints]
 workspace = true