Type Collector meta-issue

https://github.com/runtimeverification/stable-mir-json/blob/8c178ef013845510ba8287c03b01d75bc62c18a4/src/printer.rs#L490-L494

TODO

• Emit signatures for monomorphized FnDefs
  https://github.com/runtimeverification/stable-mir-json/blob/8c178ef013845510ba8287c03b01d75bc62c18a4/src/printer.rs#L534-L538
  https://github.com/runtimeverification/stable-mir-json/blob/8c178ef013845510ba8287c03b01d75bc62c18a4/src/printer.rs#L508-L514
  The resolved argument and return types get added to the collector's TyMap, but should we also add the type for the resolved function signature?

• Investigate CoroutineWitness
  https://github.com/runtimeverification/stable-mir-json/blob/8c178ef013845510ba8287c03b01d75bc62c18a4/src/printer.rs#L532-L533

• Investigate whether or not we're adding unmonomorphized/mir to the type map.
  Look into anything offered by the compiler interface like predicates, or match/print statements we can come up with to catch anything.

Start in src/printer.rs at lines 490-494, 508-514, and 532-538. Investigate signatures for monomorphized FnDefs, CoroutineWitness, and whether unmonomorphized MIR enters the type map, including compiler-interface predicates or matching/printing cases. Done means each TODO has a documented resolution and the relevant type-collection behavior is covered.