radio/vrtsim: Add CIRDB support for precomputed channel taps
Integrate Channel Impulse Response Database (CIRDB) to enable playback
of precomputed realistic channel taps in vrtsim, with runtime selection
via YAML metadata.
Features:
- Read precomputed channel taps from binary database with YAML sidecar
- Runtime enable via --vrtsim.cirdb with optional paths (cirdb_yaml, cirdb_file, cirdb_path)
- Channel parameter configuration: model_id (TDL-A..E), delay spread (ds_ns), UE speed (speed_mps)
- Fallback to existing channel model options when disabled
- Time-driven snapshot progression based on elapsed simulation time
Fixes:
- RNG initialization: Add randominit() call before gaussZiggurat()
- FlatBuffers linking: Handle both 'FlatBuffers' and 'flatbuffers' package names when working with external channel emmulator
- Address review comments: use pthread directly, update calloc_or_fail, simplify CMake
Merkebu Girmay
ccf5021072