Crosspoint/test

Host-side gtest unit tests for crosspoint-reader.

Build and run:

  cmake -S test -B build/test
  cmake --build build/test
  ctest --test-dir build/test --output-on-failure -j

Run a single suite directly:

  cmake --build build/test --target StreamingJsonParserTest
  build/test/streaming_json_parser/StreamingJsonParserTest --gtest_filter='*'

Google Test is fetched via CMake FetchContent on first configure; the pinned
version lives in test/CMakeLists.txt.