gdb: remove uses of iterate_over_inferiors in mi/mi-main.c

Replace with range-based loops.

gdb/ChangeLog:

	* mi/mi-main.c (run_one_inferior): Change return type to void, replace
	`void *` parameter with proper parameters.
	(mi_cmd_exec_run): Use range-based loop to iterate over inferiors.
	(print_one_inferior): Change return type to void, replace `void *`
	parameter with proper parameters.
	(mi_cmd_list_thread_groups): Use range-based loop to iterate over
	inferiors.
	(get_other_inferior): Remove.
	(mi_cmd_remove_inferior): Use range-based loop to iterate over
	inferiors.