Auto merge of #129385 - tgross35:more-platforms-enable-f16, r=Mark-Simulacrum

Enable `f16` tests on platforms that were missing conversion symbols

The only requirement for `f16` support, aside from LLVM not crashing and no ABI issues, is that symbols to convert to and from `f32` are available. Since the update to compiler-builtins in rust-lang/rust#125016, we now provide these on all platforms.

This also enables `f16` math since there are no further requirements.

Still excluded are platforms for which LLVM emits infinitely-recursing code.

try-job: arm-android
try-job: test-various
try-job: x86_64-fuchsia

Author: bors