Integrate otel-cpp library with the build system

[wazir-ahmed]

Closes #4985.

[gemini-code-assist]

Summary of Changes

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This pull request introduces the OpenTelemetry C++ client library and its required dependencies (Abseil, Protobuf, JSON) into the project's build infrastructure. It updates the Makefiles to fetch, build, and install these new dependencies locally, and adjusts the compilation and linking flags across the project to incorporate them. Additionally, it refactors the include paths for the JSON library to align with a standard installation structure.

Highlights

• OpenTelemetry Integration: Integrated the OpenTelemetry C++ client library (otel-cpp) into the project's build system.
• Dependency Management: Added build rules for OpenTelemetry and its core dependencies (Abseil, Protobuf, JSON) within the deps/Makefile.
• Build System Updates: Modified main, library, source, and test Makefiles to include necessary paths and link against the newly added OpenTelemetry and dependency libraries.
• Include Path Refactoring: Updated numerous source and header files to use standard include paths (e.g., nlohmann/json.hpp) for the JSON library, reflecting its installation into a designated include directory.

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[gemini-code-assist]

Code Review

This pull request integrates the OpenTelemetry C++ library and its dependencies (Abseil, Protobuf, updated cURL, nlohmann/json) into the build system. Key changes involve updating deps/Makefile to download, build, and install these libraries, modifying src/Makefile and lib/Makefile to include new header and library paths, and updating C++ source files to use the new include path for nlohmann/json.

Several potential issues were identified, primarily concerning the directory path assumptions for extracted tarballs in deps/Makefile, a possible typo in src/Makefile affecting cURL include paths on Linux, and a missing cleanup step in deps/Makefile. The changes to C++ include paths for the JSON library are generally good, assuming the dependency is correctly built and its headers are placed as expected.