Rollup merge of rust-lang#77122 - ecstatic-morse:const-fn-arithmetic, r=RalfJung,oli-obk

Add `#![feature(const_fn_floating_point_arithmetic)]`

cc rust-lang#76618

This is a template for splitting up `const_fn` into granular feature gates. I think this will make it easier, both for us and for users, to track stabilization of each individual feature. We don't *have* to do this, however. We could also keep stabilizing things out from under `const_fn`.

cc @rust-lang/wg-const-eval
r? @oli-obk

Author: RalfJung

core/src/lib.rs

@@ -82,6 +82,7 @@
 #![feature(const_pin)]
 #![feature(const_fn_union)]
 #![feature(const_fn)]
+#![cfg_attr(not(bootstrap), feature(const_fn_floating_point_arithmetic))]
 #![feature(const_generics)]
 #![feature(const_option)]
 #![feature(const_precise_live_drops)]

std/src/lib.rs

@@ -236,6 +236,7 @@
 #![feature(clamp)]
 #![feature(concat_idents)]
 #![feature(const_cstr_unchecked)]
+#![cfg_attr(not(bootstrap), feature(const_fn_floating_point_arithmetic))]
 #![feature(const_fn_transmute)]
 #![feature(const_fn)]
 #![feature(const_ip)]