Reconsider making rust nightly job standalone

I feel that isolating this job from not re-using the other workflows makes it more fragile and more likely to break and not cover new tests as they are added. I realize this makes creating this file much easier so maybe its worth the trade off and we can try it for a little while

_Originally posted by @jsturtevant in https://github.com/hyperlight-dev/hyperlight/pull/1104#discussion_r2612133041_