Internal simplifications to constructing datatypes (#8519)

Internal simplifications to constructing datatypes (#8519)

In preparation for #8511.

This makes it so that unresolved sorts are automatically inferred when constructing datatypes at the NodeManager level. This is in preparation for simplifying the API.

Changes:
(1) NodeManager is cleaned so that unresolved types are automatically inferred and are not a part of its public interface. Internal code generating datatypes is simplified as a result.
(2) Adds necessary utilities to TypeNode and cleans an unused flag
(3) The parser is cleaned to not track unresolved sorts in an ad-hoc manner.
(4) The API is patched to use the simpler interface.