Module traits tracking issue

[LPTK]

Required changes

• Make "require captures" use the same instance (see CapturingTraitImpls.mls)

Features to add support for:

• Add using clauses as an alternative to require that does not request a unique instance

Tests/use cases to add to the test suite:

• A parser with mutually-recursive functions
  • from different trait: would probably cause cycle error;
  • from the same trait: can we still do partial implementations?