PR for this proposed refactoring is now up, with a review requested from Mark: https://github.com/python/cpython/pull/27525/

The PR mostly follows what I originally posted, except that I went with _Py_execution_frame and _PyExecFrame for the struct and typedef names, since these are present in a public header.

The outdated GDB hooks I found were in the gdbinit example file, rather than the actual libpython.py file that test_gdb covers. I suspect the gdbinit example will need further adjustments to actually work with Python 3.11, so rather than fully updating the implementation dependent pieces, I just added a comment suggesting it be checked after the interpreter optimisation development for 3.11 settles down.