Remove deprecated C API objects slated for removal in 3.15

[picnixz]

Proposal:

This issue serves as a tracker for removing the following parts of the C API:

• Global configuration variables: #133654
• Process-wide parameters: #133661
• PyImport_ImportModuleNoBlock: #133655
• PyWeakref_GetObject and PyWeakref_GET_OBJECT: #133657
• Functions to configure Python's initialization (PySys_Set* & co)
• Py_UNICODE_WIDE and Py_UNICODE type

Tracked separately:

• vendored copy of libmpdecimal: #115119. (deferred to Python 3.16)
• PyUnicode_As{Encoded,Decoded}{Object,Unicode}: #133610 cc @StanFromIreland
• PySys_ResetWarnOptions Remove deprecated PySys_ResetWarnOptions C-API function #138886 cc @sobolevn

I'll take care of doing the other deprecation removals and update c-api-pending-removal-in-3-15.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-133644: remove deprecated global configuration variables #133654
• gh-133644: remove deprecated PyImport_ImportModuleNoBlock #133655
• gh-133644: remove PyWeakref_GetObject and PyWeakref_GET_OBJECT #133657
• gh-133644: remove deprecated Python initialization getter functions #133661
• gh-133644: Avoid deprecated Py_SetProgramName() in _testembed.c #133665
• gh-133644: update Py_InteractiveFlag deprecation notice #133749
• [3.14] gh-133644: update Py_InteractiveFlag deprecation notice (GH-133749) #133751
• [3.13] gh-133644: update Py_InteractiveFlag deprecation notice (GH-133749) #133752
• gh-133644: Remove PySys_SetArgv* for 3.15 #136277
• gh-138886: Remove deprecated PySys_ResetWarnOptions C-API function #138887

[skirpichev]

There is still the libmpdecimal removal, but I'll track it in a separate issue.

See #115119