PR jit/64166: Add methods to gcc::dump_manager needed by JIT testing

PR jit/64166: Add methods to gcc::dump_manager needed by JIT testing

gcc/ChangeLog:
	PR jit/64166
	* dumpfile.c (gcc::dump_manager::get_dump_file_info_by_switch):
	New function.
	(gcc::dump_manager::get_dump_file_name): Split out bulk of
	implementation into a new overloaded variant taking a
	dump_file_info *.
	* dumpfile.h (gcc::dump_manager::get_dump_file_info_by_switch):
	New function.
	(gcc::dump_manager::get_dump_file_name): New overloaded variant of
	this function, taking a dump_file_info *.

From-SVN: r218520