Rollup merge of #139974 - Patrick-6:change-visibility, r=RalfJung

Change `InterpCx::instantiate*` function visibility to pub

For some ongoing work in Miri we need to be able to access `instantiate_from_current_frame_and_normalize_erasing_regions` and `instantiate_from_frame_and_normalize_erasing_regions` on `InterpCx`.

r? `@RalfJung`

Author: matthiaskrgr