refactor(tty): tty.request() #39489

Problem:
- Various `TermRequest` handlers which all do similar things.
- `tty.query` is specific to `XTGETTCAP DCS`, can't be reused for other kinds of terminal queries.

Solution:
Provide `tty.request()`.

runtime/lua/vim/_init_packages.lua

@@ -60,6 +60,7 @@ vim._submodules = {
   iter = true,
   re = true,
   text = true,
+  tty = true,
   provider = true,
 }