Fix keycode parameter extraction to match the new DD keycodes (#18977)

* Add macros to extract parameters from keycode values

Implement both encoding and decoding for keycodes like TO(layer) or
LM(layer, mod) in one place, so that the decoding won't get out of sync
with the encoding.

While at it, fix some macros for creating keycode values that did not
apply the appropriate masks to parameters (and therefore could allow the
result to be out of range if a wrong parameter was passed).

* keymap_common: Use extraction macros for keycodes

* pointing_device_auto_mouse: Use extraction macros for keycodes

Fixes #18970.

* process_autocorrect: Use extraction macros for keycodes

* process_caps_word: Use extraction macros for keycodes

(Also fix a minor bug - SH_TG was not handled properly)

* process_leader: Use extraction macros for keycodes

(Technically the code is not 100% correct, because it always assumes
that the LT() or MT() action was a tap, but it's a separate issue that
already existed before the keycode changes.)

* process_unicode: Use extraction macros for keycodes

* process_unicodemap: Use extraction macros for keycodes

quantum/process_keycode/process_unicode.c

@@ -21,7 +21,7 @@
 bool process_unicode(uint16_t keycode, keyrecord_t *record) {
     if (record->event.pressed) {
         if (keycode >= QK_UNICODE && keycode <= QK_UNICODE_MAX) {
-            register_unicode(keycode & 0x7FFF);
+            register_unicode(QK_UNICODE_GET_CODE_POINT(keycode));
         }
     }
     return true;