Convert _ctypes extension module to multi-phase init

[neonene]

Feature or enhancement

Proposal:

This issue is available to keep track of PRs, following the heap type conversion completed at #114314.

TODO:

• [ ] Make free_list in malloc_closure.c per-module variables. rejected
• Fix intentional memory leaks of StgInfo during a finalization: comment.
• Enable Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED(DONE): comment.
  FUTURE?: Py_MOD_PER_INTERPRETER_GIL_SUPPORTED after a compatible PyGILState_Ensure() is introduced, see also the links below.

Links to documents:

• libffi: a foreign function interface library
• libffi - GitHub

Links to previous discussion of this feature:

• Isolate Stdlib Extension Modules #103092
• Convert _ctypes static types (and the "meta class") to heap types #114314
• PyGILState_Ensure() for sub-interpreters:
  • [subinterpreters] Make the PyGILState API compatible with subinterpreters #59956
  • [subinterpreters] Make the PyGILState API compatible with multiple interpreters #55124
    • _ctypes patch (2011)

Linked PRs

• gh-117142: ctypes: Unify meta tp slot functions #117143
• gh-117142: Port _ctypes to multi-phase init #117181
• gh-117142: ctypes: Migrate global vars to module state #117189
• gh-117142: ctypes: Clean up globals-to-fix.tsv #117544
• gh-117142: ctypes: Migrate global closure freelist to thunk-type state #117874
• gh-117142: ctypes: Migrate global closure freelist to module state #117875
• gh-117142: ctypes: Fix memory leak of StgInfo #118139
• gh-117142: Slightly hacky fix for memory leak of StgInfo #119424
• [3.13] gh-117142: Slightly hacky fix for memory leak of StgInfo (GH-119424) #119468
• gh-117142: Support Importing ctypes in Isolated Interpreters #119991
• [3.13] gh-117142: Support Importing ctypes in Isolated Interpreters (gh-119991) #120008