Move some std tests to integration tests
Unit tests directly inside of standard library crates require a very fragile way of building that is hard to reproduce outside of bootstrap.
Follow up to https://github.com/rust-lang/rust/pull/133859
Searching "fma" in the Rust documentation returns results for
`intrinsics::fma*`, but does not point to the user-facing `mul_add`. Add
aliases for `fma*` and the IEEE operation name `fusedMultiplyAdd`. Add
the IEEE name to `sqrt` as well, `squareRoot`.
Some float methods are now `const fn` under the `const_float_methods` feature gate.
In order to support `min`, `max`, `abs` and `copysign`, the implementation of some intrinsics had to be moved from Miri to rustc_const_eval.
This adds missing functions for math operations on the new float types.
Platform support is pretty spotty at this point, since even platforms
with generally good support can be missing math functions.
`std/build.rs` is updated to reflect this.
This adds everything that was directly or transitively blocked on const
arithmetic for these types, which was recently merged.
Since const arithmetic is recent, most of these need to be gated by
`bootstrap`.
Anything that relies on intrinsics that are still missing is excluded.
