What does this implement/fix? Explain your changes.

This introduces a new PyType class (similar to PyInt, but for types). It can:

• wrap existing PyObject, that points to a type
• create a new heap type from spec (TypeSpec class)

Does this close any currently open issues?

It is WIP on #1033
It is related to #1196

Checklist

Check all those that are applicable and complete.

• Make sure to include one or more tests for your change
• Updated the CHANGELOG