Use filtered output in ordinary commands

Many otherwise ordinary commands choose to use unfiltered output
rather than filtered.  I don't think there's any reason for this, so
this changes many such commands to use filtered output instead.

Note that complete_command is not touched due to a comment there
explaining why unfiltered output is believed to be used.

gdb/exec.c

@@ -378,7 +378,7 @@ exec_file_attach (const char *filename, int from_tty)
   if (!filename)
     {
       if (from_tty)
-	printf_unfiltered (_("No executable file now.\n"));
+	printf_filtered (_("No executable file now.\n"));
 
       set_gdbarch_from_file (NULL);
     }