Split unicode.c tests of _testcapi into two parts: limited C API
tests in _testlimitedcapi and non-limited C API tests in _testcapi.
Update test_codecs.
Remove private _PyUnicode_TransformDecimalAndSpaceToASCII() and other
private _PyUnicode C API functions: move them to the internal C API
(pycore_unicodeobject.h). No longer most of these functions.
Replace _testcapi.unicode_transformdecimalandspacetoascii() with
_testinternal._PyUnicode_TransformDecimalAndSpaceToASCII().
* Support for conversion specifiers o (octal) and X (uppercase hexadecimal).
* Support for length modifiers j (intmax_t) and t (ptrdiff_t).
* Length modifiers are now applied to all integer conversions.
* Support for wchar_t C strings (%ls and %lV).
* Support for variable width and precision (*).
* Support for flag - (left alignment).
- Move PyUnicode tests to a separate file
- Add some more tests for PyUnicode_FromFormat
Co-authored-by: philg314 <110174000+philg314@users.noreply.github.com>