Rollup merge of #146737 - RalfJung:f16-f128-miri, r=tgross35

f16_f128: enable some more tests in Miri

For some reason, a bunch of tests were disabled in Miri that don't use any fancy intrinsics. Let's enable them.

I verified this with `./x miri library/core --no-doc -- float`.

r? `@tgross35`

Author: Zalathar