Description

Add C language binding (ddog_trace_*) wrapping the C++ tracing library for integration from C-based projects.
Follows Datadog's ddog_ naming convention from libdatadog. Gated behind BUILD_C_BINDING=OFF.

Motivation

Enable C-based projects to use dd-trace-cpp without a C++ dependency at the call site.

Building and Testing

cmake -B build -DBUILD_C_BINDING=ON -DDD_TRACE_BUILD_TESTING=ON
cmake --build build -j
./build/binding/c/test_c_binding