Fix incorrect replacements in Py_ to Ty_ renaming

Fixed several macros and constants that should not have been renamed:
- _Py_CAST, _Py_NULL, _Py_RVALUE (internal utility macros)
- Py_UNUSED (unused parameter macro)
- Py_EQ, Py_NE, Py_LT, Py_LE, Py_GT, Py_GE (comparison constants)
- Py_RETURN_* macros (NONE, TRUE, FALSE, NOTIMPLEMENTED, RICHCOMPARE)
- Py_READONLY, Py_ULL, Py_CONTEXT_SWITCHED
- TyGC_Head in generated clinic files

Build is still in progress with some remaining issues to resolve.

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

Include/methodobject.h

@@ -45,7 +45,7 @@ typedef PyCFunctionFastWithKeywords _PyCFunctionFastWithKeywords;
 // "void func(void)" type to prevent compiler warnings.
 //
 // If a function is declared with the METH_NOARGS calling convention, it must
-// have 2 parameters. Since the second parameter is unused, Ty_UNUSED() can be
+// have 2 parameters. Since the second parameter is unused, Py_UNUSED() can be
 // used to prevent a compiler warning. If the function has a single parameter,
 // it triggers an undefined behavior when Python calls it with 2 parameters
 // (bpo-33012).