gh-111972: unicode: Make ucnhash_capicapsule initialization thread-safe

[Eclips4]

• Issue: unicode: make ucnhash_capi initialization thread-safe in --disable-gil builds #111972

[colesbury]

I think we also need to handle the case 'N' in _PyUnicode_DecodeUnicodeEscapeInternal.

[Eclips4]

Should we do something with _PyUnicode_Fini?

cpython/Objects/unicodeobject.c

Lines 15445 to 15460 in 14fd86a

	void
	_PyUnicode_Fini(PyInterpreterState *interp)
	{
	struct _Py_unicode_state *state = &interp->unicode;
	// _PyUnicode_ClearInterned() must be called before _PyUnicode_Fini()
	assert(get_interned_dict(interp) == NULL);
	_PyUnicode_FiniEncodings(&state->fs_codec);
	// bpo-47182: force a unicodedata CAPI capsule re-import on
	// subsequent initialization of interpreter.
	interp->unicode.ucnhash_capi = NULL;
	unicode_clear_identifiers(state);
	}

[colesbury]

_PyUnicode_Fini looks fine. I don't think it needs any special handling.

[colesbury]

@erlend-aasland, would you please review this when you get a chance?

[erlend-aasland]

Thanks for the PR, Kirill, and thanks for the review, Sam!