Phase 3 tracking issue

[bvisness]

The entry requirements for phase 3 are:

• Test suite has been updated to cover the feature in its forked repo.
• The test suite should run against some implementation, though it need not be the reference interpreter.
• Updates on the actual spec document and reference interpreter are NOT yet required (but can happen earlier).

Since this is already widely implemented, the main thing will be to resolve #4 and check the remaining boxes.

• Support round-tripping parameter names from function type definitions #4
• Adding tests #2