Convert _ctypes static types (and the "meta class") to heap types

Feature or enhancement

The _ctypes extension implements types as static types. They should be converted to heap types: see issue gh-103092 for the rationale.

Problem: the PyCStgDict type is kind of special, it's a "metaclass" which creates a new class and then replaces the class namespace (type dict) with a custom "stgdict". See the PyCStructType_new() function.

Previous attempts to convert _ctypes types to heap types:

• April 2023: PR gh-103092: Adapt _ctypes's PyCStgDict type to heap type #103932
• January 2024: PR gh-103092: Port some _ctypes data types to heap types #113630

Linked PRs

• gh-114314: Move types to ctypes_state #114316
• gh-114314: Avoid possibly invalid args when initializing a ctypes meta type #114740
• gh-114314: ctypes: remove stgdict and switch to heap types #116458