feat(terminal): add support for kitty keyboard protocol

This commit adds basic support for the kitty keyboard protocol to
Neovim's builtin terminal. For now only the first mode ("Disambiguate
escape codes") is supported.

test/functional/terminal/buffer_spec.lua

@@ -629,6 +629,14 @@ describe('terminal input', function()
   -- TODO(bfredl): getcharstr() erases the distinction between <C-I> and <Tab>.
   -- If it was enhanced or replaced this could get folded into the test above.
   it('can send TAB/C-I and ESC/C-[ separately', function()
+    if
+      skip(
+        is_os('win'),
+        "The escape sequence to enable kitty keyboard mode doesn't work on Windows"
+      )
+    then
+      return
+    end
     clear()
     local screen = tt.setup_child_nvim({
       '-u',