[3.13] Doc/c-api/memory.rst: extend --without-pymalloc doc with ASan information (GH-136790) (#136799)

Extends the documentation for disabling pymalloc with the `--without-pymalloc` flag regarding why it is worth to use it when enabling AddressSanitizer for Python build (which is done, e.g., in CPython's CI builds).


(cherry picked from commit d19bb4471331ca2cb87b86e4c904bc9a2bafb044)

Co-authored-by: Disconnect3d <dominik.b.czarnota@gmail.com>
Co-authored-by: Petr Viktorin <encukou@gmail.com>