UbDiag two-layer integration

[qinyufei63]

Description

将 Mooncake 对 UbDiag 的编译期系统包硬依赖改为基于 UBDIAG_DISABLE 的两层集成：

• 默认 Layer 0：FetchContent 获取固定版本头文件，定义 UBDIAG_DISABLE，PerfPoint 编译为空函数，不构建或链接 libubdiag
• 可选 Layer 1：通过 -DMOONCAKE_ENABLE_UBDIAG=ON 同步构建 libubdiag.so 和同源码 CLI
• 固定从 LinQuickDev/ubdiag 拉取 v0.5.1，并支持 MOONCAKE_UBDIAG_SOURCE_DIR 离线源码
• 保留 P99/P999/P9999、PerfLog 和 CSV；关闭 OB memory/cache、MemPoint、CachePoint
• 使用函数作用域隔离 UbDiag 的通用 BUILD_TESTS/BUILD_EXAMPLES，不修改 Mooncake 自身构建选项
• Store、Transfer Engine、Integration 和 P2P Store 统一消费 UbDiag::ubdiag_lib
• 本 PR 替代 Supercache dev extern mock clean #10 中的三层 submodule/system/mock 方案；不引入 UbDiag submodule 或系统包 fallback

Module

• Transfer Engine (mooncake-transfer-engine)
• Mooncake Store (mooncake-store)
• Mooncake EP (mooncake-ep)
• Mooncake PG (mooncake-pg)
• Integration (mooncake-integration)
• P2P Store (mooncake-p2p-store)
• Python Wheel (mooncake-wheel)
• Common (mooncake-common)
• Mooncake RL (mooncake-rl)
• CI/CD
• Docs
• Other

Type of Change

• Bug fix
• New feature
• Refactor
• Breaking change
• Documentation update
• Performance improvement
• Other

How Has This Been Tested?

Test commands:

git diff --check
bash -n mooncake-p2p-store/build.sh

Test results:

• 正式分支仅包含 7 个已审查的集成与文档文件
• DISABLE/vendored CMake 路径已按 UbDiag v0.5.1 target 静态复核
• UbDiag 固定为 tag v0.5.1 / commit 705c6c37da45df2be4bc64c134dca0b7f30b2113
• 完整 DISABLE/vendored 编译、benchmark、PerfLog/P99/CSV 运行验证正在进行，将在合入前补充

Checklist

• I have performed a self-review of my own code
• I have formatted my code using ./scripts/code_format.sh
• I have run pre-commit run --all-files and all hooks pass
• I have updated the documentation (if applicable)
• I have added tests to prove my changes are effective
• For changes >500 LOC: I have filed an RFC issue

AI Assistance Disclosure

• No AI tools were used
• AI tools were used (implementation review, documentation alignment, and validation script assistance)

The human submitter has reviewed the changes and is responsible for understanding and defending them.

[qinyufei63]

此 PR 误从临时分支创建，已改由指定开发分支 supercache_dev_ubdiag 提交：#13。关闭本 PR，后续以新 PR 为准。