refactor(tui): use nvim_echo() for verbose terminfo

This is needed for #18375 for the obvious reasons.
note: verbose_terminfo_event is only temporarily needed
until the full TUI process refactor is merged.

src/nvim/api/keysets.lua

@@ -219,5 +219,8 @@ return {
   cmd_opts = {
     "output";
   };
+  echo_opts = {
+    "verbose";
+  };
 }