Adds TRAIT_SKELETONIZED to Ancient Skeletons

[iramoye]

What Does This PR Do

Adds TRAIT_SKELETONIZED to Ancient Skeletons. This means that Ancient Skeletons will now be able to play the xylophone on themselves by clicking themselves on help intent while not wearing a jumpsuit or outer suit.

Why It's Good For The Game

Skeletons should have the trait specific to skeletons.
Fixes #31405

Testing

Compiled. Clicked self to trigger xylophone.

Declaration

• I confirm that I either do not require pre-approval for this PR, or I have obtained such approval and have included a screenshot to demonstrate this below.

Changelog

🆑
add: Ancient Skeletons can play the xylophone by clicking themselves on help intent with no jumpsuit or outer suit.
/:cl:

[CRUNCH-Borg]

/mob/living/carbon/human/revive() will strip TRAIT_SKELETONIZED from skeletons if used on them.

It is probably better to add an alternative check to the xylophone conditional that checks for either TRAIT_SKELETONIZED or isskeleton(H).