This change is somewhat extensive, since it affects MIR -- since this is called to determine Copy vs Move -- so any test that's `no_core` needs to actually have the normal `impl`s it uses.
This PR adds ability for the target specifications to specify frame
pointer emission type that's not just “always” or “whatever cg decides”.
In particular there's a new mode that allows omission of the frame
pointer for leaf functions (those that don't call any other functions).
We then set this new mode for Aarch64-based Apple targets.
Fixes#86196