Move DrainFromAsync to tests, add in-memory benchmarks
- Moved AsyncPipeReaderInputExtensions.DrainFromAsync from the main framework to test-only assembly; no longer public API.
- Removed AcBinaryDeserializer.DeserializeFromPipeReaderAsync<T> from public API; tests now inline drain+deserialize logic.
- Added AcBinaryInMemoryPipeBenchmark and AcBinaryInMemoryRawByteArrayBenchmark to complete 2x2 transport × wire-format benchmark matrix.
- Refactored benchmark runner for interactive menu, settings, and CLI parsing.
- Expanded XML docs for AsyncPipeReaderInput and AsyncPipeWriterOutput to clarify push-pattern and real-world usage.
- Updated BINARY_ASYNCPIPE_TODO.md and related docs to reflect these changes.
