build(test): generate per-file brpc cc_test to improve Bazel UT coverage

[XueSongTap]

What problem does this PR solve?

Part: #2904

Problem Summary:

• BUILD.bazel 只编译了极少数 brpc 单元测试；
• 直接 glob(["brpc_*_unittest.cpp"]) 会把多个含 int main() 的源文件链接进同一可执行文件，引发 duplicate symbol: main，导致其余测试无法构建。
• CMake 已覆盖全部 UT。为了让两套构建结果一致，需要在 Bazel 侧同样编译（并可执行）全部 brpc 单测文件。
• 其中 test/brpc_http_rpc_protocol_unittest.cpp的修改是为了兼容bazel指定的 更高的proto版本 基于Bazel编译的UT不完善 #2904 (comment)

What is changed and the side effects?

Changed:

位置	变更	说明
test/brpc_unit_test.bzl	新增	提供 generate_brpc_unit_tests() 宏：- 输入 任意 .cpp 列表 → 输出 “一文件一 cc_test” + 聚合 test_suite。
test/BUILD.bazel	新增brpc_test UT 部分	一次宏调用即可把 全部 brpc_*_unittest.cpp 生成 多个 cc_test；逻辑与 test/CMakeLists.txt的 brpc/test/CMakeLists.txt Line 253 in c24e641 foreach(BRPC_UT ${BRPC_UNITTESTS}) 一致

Side effects:

• Performance effects:无

• Breaking backward compatibility: 无

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[chenBright]

Is it possible to use bazel tests with github workflows?

[XueSongTap]

Sure, i"ll work on workflow

[wwbmmm]

This code looks no problem, but I don't know why the ci-linux workflow is not runned…

[chenBright]

StackTraceTest.find_symbol seems to fail in clang14. It is recommended to use clang12 with sudo apt-get install -y clang-12 lldb-12 lld-12.

[chenBright]

And --action_env=CC=clang-12.

[chenBright]

Build on Macos has been fixed in master. Please update and rebase master.