This introduces `xmlo-experimental` for `--emit`, allowing the new parser to
be toggled selectively for individual packages. This has a few notable
benefits:
1. We'll be able to conditionally compile packages as they are
supported (TAMER will target specific packages in our system to try to
achieve certain results more quickly);
2. This cleans up the code a bit by removing awkward gated logic, allowing
natural abstractions to form; and
3. Removing the compile-time feature flag ensures that the new features
are always built and tested; there are fewer configuration combinations
to test.
DEV-13162
Mike Gerwitz