Rollup merge of #123087 - tgross35:clippy-f16-f128-check-stubs, r=blyxyas

Change `f16` and `f128` clippy stubs to be nonpanicking

It turns out there is a bit of a circular dependency - I cannot add anything to `core` because Clippy fails, and I can't actually add correct Clippy implementations without new implementations from `core`.

Change some of the Clippy stubs from `unimplemented!` to success values and leave a FIXME in their place to mitigate this.

Fixes <rust-lang/rust#122587>

Author: matthiaskrgr