Resolves rdar://140298287
ExtractAPI's support for printing Objective-C category extensions from
other modules emits symbol graphs with an
`ExtendedModule@HostModule.symbols.json`. However, this is backwards
from existing symbol graph practices, causing issues when these symbol
graphs are consumed alongside symbol graphs generated with other tools
like Swift. This PR flips the naming scheme to be in line with existing
symbol graph tooling.
Reenables b31414bf4f9898f7817a9fcf8a91f62ec26f3eaf.
Also adds a new warning for missing `--symbol-graph-dir` arg when
`--emit-extension-symbol-graphs` is provided. This also reverts the
commit that removed.
This extends ExtractAPI to take into account symbols defined in categories to types defined in an external module.
This introduces 2 new command line flags, `--symbol-graph-dir=DIR` and `--emit-extension-symbol-graphs`, when used together this generates additional symbol graph files at `DIR/ExtendedModule@ProductName.symbols.json` for each external module that is extended in this way.
Additionally this makes some cleanups to tests to make them more resilient and cleans up the `APISet` data structure.
