patch 8.2.0256: time and timer related code is spread out

Problem:    Time and timer related code is spread out.
Solution:   Move time and timer related code to a new file. (Yegappan
            Lakshmanan, closes #5604)

src/ex_cmds.c

@@ -1678,20 +1678,6 @@ append_redir(
 		(char *)opt, (char *)fname);
 }
 
-/*
- * Return the current time in seconds.  Calls time(), unless test_settime()
- * was used.
- */
-    time_T
-vim_time(void)
-{
-# ifdef FEAT_EVAL
-    return time_for_testing == 0 ? time(NULL) : time_for_testing;
-# else
-    return time(NULL);
-# endif
-}
-
 /*
  * Implementation of ":fixdel", also used by get_stty().
  *  <BS>    resulting <Del>