Add Thrift support to build system and CI

[Copilot]

Integrates Apache Thrift 0.11.0 into the build infrastructure to enable Thrift protocol support in brpc.

Changes

• CI workflow: Added Thrift 0.11.0 installation step in GitHub Actions, installing to /usr for unified dependency management
• Build configuration: Updated config_brpc.sh to detect Thrift binary and libraries when --with-thrift is enabled
• Test infrastructure: Modified test/Makefile to compile Thrift-generated sources from echo.thrift, producing gen-cpp/ directory
• Dependency consolidation: Moved gperftools and abseil-cpp installation from custom prefixes to /usr to simplify header/lib path management

Build system integration

The Thrift compiler generates C++ sources at build time:

gen-cpp/echo_types.cpp gen-cpp/echo_types.h: echo.thrift
	$(THRIFT) --gen cpp $<

Generated files are automatically included in test builds and excluded via .gitignore.

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