refactor(exit): pass error message to preserve_exit() (#22097)

Problem:
1. Some calls to preserve_exit() don't put a message in IObuff, so the
   IObuff printed by preserve_exit() contains unrelated information.
2. If a TUI client runs out of memory or receives a deadly signal, the
   error message is shown on alternate screen and cannot be easily seen
   because the TUI exits alternate screen soon afterwards.

Solution:
Pass error message to preserve_exit() and exit alternate screen before
printing it.

Note that this doesn't fix the problem that server error messages cannot
be easily seen on exit. This is tracked in #21608 and #21843.

src/nvim/lua/executor.c

@@ -211,9 +211,7 @@ static int nlua_luv_cfpcall(lua_State *lstate, int nargs, int nresult, int flags
   if (status) {
     if (status == LUA_ERRMEM && !(flags & LUVF_CALLBACK_NOEXIT)) {
       // consider out of memory errors unrecoverable, just like xmalloc()
-      os_errmsg(e_outofmem);
-      os_errmsg("\n");
-      preserve_exit();
+      preserve_exit(e_outofmem);
     }
     const char *error = lua_tostring(lstate, -1);