Rollup merge of #137674 - heiher:enable-f16-loong, r=tgross35

Enable `f16` for LoongArch

Blocked on https://github.com/rust-lang/compiler-builtins/pull/770

r? ```@tgross35```

Tracking issue for f16: https://github.com/rust-lang/rust/issues/116909

try-job: dist-loongarch64-linux
try-job: dist-loongarch64-musl