It is not a distinct result returned by `swiftscan_compiler_supported_arguments_query` and `swiftscan_compiler_supported_features_query`, not owned by any other type, so it must be disposed of by the clients.
For the client library (`libSwiftDriver`), this is critical for multiplexing library instances, and for compatibility with different versions of `libSwiftDrvier`.
Resolves rdar://73631930
Adds a C API layer consisting of:
- Data structures used to represent in-memory result of dependency scanning
- Opaque dependency scanner tool (C wrapper for `DependencyScanningTool`)
Refactors `ScanDependencies.cpp` to produce dependency scanning result in the form of the above binary format.