Handle new F16 and F128 types

[zhassan-aws]

This is a tracking issue for adding support for the new 16-bit and 128-bit floating-point types that are being added to Rust.

Upstream tracking issue: rust-lang/rust#116909

[tgross35]

Just FYI these are super unstable and will basically ICE if you do anything at all with them. Hopefully that will change in a couple weeks.

Thanks for being on top of it!

[jaisnan]

Some support is being added as of this PR: #3306.
@zhassan-aws is this enough to close the issue or should we keep the issue open till they're fully stable?

[tgross35]

FYI most of the ICE paths have been removed (const time as casting being the last thing until rust-lang/rust#127032). Platform support is still weak though, we're having some problems getting compiler_builtins updated.

See https://github.com/rust-lang/rust/blob/c4c0897a262d42f26f89aaca16ed52457f6a4f05/library/std/build.rs#L78-L127 if you need a rough estimate of what works where (I'll be keeping that up to date as more support gets added)