gh-140815: Fix faulthandler for invalid/freed frame (#140921)

faulthandler now detects if a frame or a code object is invalid or
freed.

Add helper functions:

* _PyCode_SafeAddr2Line()
* _PyFrame_SafeGetCode()
* _PyFrame_SafeGetLasti()

_PyMem_IsPtrFreed() now detects pointers in [-0xff, 0xff] range
as freed.