Remove deprecated C API objects slated for removal in 3.15

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 https://github.com/python/cpython/issues/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-133654
• gh-133655
• gh-133657
• gh-133661
• gh-133665
• gh-133749
• gh-133751
• gh-133752
• gh-136277
• gh-138887

Review the remaining unchecked C API items in this tracker and the c-api-pending-removal-in-3-15 list. The linked pull requests show that much of the work is already underway; done would mean completing the outstanding removals and updating the pending-removal list.