vim-patch:8.2.4911: the mode #defines are not clearly named (#18499)

Problem:    The mode #defines are not clearly named.
Solution:   Prepend MODE_.  Renumber them to put the mapped modes first.
249591057b

A hunk from the patch depends on patch 8.2.4861, which hasn't been
ported yet, but that should be easy to notice.

src/nvim/debugger.c

@@ -83,7 +83,7 @@ void do_debug(char_u *cmd)
   emsg_silent = false;          // display error messages
   redir_off = true;             // don't redirect debug commands
 
-  State = NORMAL;
+  State = MODE_NORMAL;
   debug_mode = true;
 
   if (!debug_did_msg) {