Invert Process_compare resolution so that superclass matches run first

* This removes duplicated code that adjusts the sort direction from every
  OS-specific folder.
* Most fields in a regular htop screen are OS-independent, so trying
  Process_compare first and only falling back to the OS-specific
  compareByKey function if it's an OS-specific field makes sense.
* This will allow us to override the sortKey in a global way without having
  to edit each OS-specific file.

Process.c

@@ -555,6 +555,6 @@ long Process_compare(const void* v1, const void* v2) {
    case USER:
       return SPACESHIP_NULLSTR(p1->user, p2->user);
    default:
-      return SPACESHIP_NUMBER(p1->pid, p2->pid);
+      return Process_compareByKey(p1, p2, key);
    }
 }