[lworld] RFR: 8244092: [lworld] TestC2CCalls segfaults in frame::sender_for_compiled_frame with ZGC

[Roland Westrelin]

> Stack slot containing real_frame_size is trashed by ZCG barrier code in scalarized entry of C1 compiled code. As a
> result, we crash during stack walking. We should re-set it before jumping to the verified entry. Also refactored the
> related code and added an assert to catch this.

Ok.

Roland.