Revert "PR fortran/95689 - ICE in check_sym_interfaces, at fortran/interface.c:2015"

Revert "PR fortran/95689 - ICE in check_sym_interfaces, at fortran/interface.c:2015"

With submodules, name mangling of interfaces may result in long internal
symbols overflowing an internal buffer.  We now check that we do not
exceed the enlarged buffer size.

gcc/fortran/
	PR fortran/95689
	* interface.c (check_sym_interfaces): Enlarge temporary buffer,
	and add check on length on mangled name to prevent overflow.

gcc/testsuite/
	PR fortran/95689
	* gfortran.dg/pr95689.f90: New test.

	(reverts the cherry-pick from commit 62c0c0ea7bfb6f8f6b8d767b05120cafb6823da6)