[RFC][flang] Trampolines for internal procedures. (#66157)

I would like to start a discussion about the ways for modifying
the current trampolines approach for Fortran internal procedures
used as actual arguments or pointer targets.

As Peter Klausler noted before the current approach implies security
risks due to writeable and executable stack requirement. We may need
to agree on a new scheme that does not have this issue.

Author: vzakhari