bug#57115: emacs 29 ~commandp~ check function ~find-file~ loop without termination while ~find-file~ is adviced nested up to 20 level

[Stefan Monnier]

> I'm not quite sure what this code snippet is attempting to achieve, but
> it does hang in Emacs 29, and it didn't in Emacs 28.

It doesn't really hang: in my tests it takes ~1s for 12 pieces of
advice, and 3x slower for every additional advice, so it should finish
in about 2h :-)

Should be fixed on `master` now.


        Stefan