Const-stabilize `const_int_ops` + `const_ip` r? @oli-obk ## Note for relnotes: This PR includes https://github.com/rust-lang/rust/pull/57105. I've added T-lang since this affects intrinsics and the operational semantics of Rust's `const fn` fragment. ## Stable APIs proposed for constification + `const_int_ops`: + `count_ones` + `count_zeros` + `leading_zeros` + `trailing_zeros` + `swap_bytes` + `from_be` + `from_le` + `to_be` + `to_le` + `const_ip` + `Ipv4Addr::new` ## Unstable APIs constified + `const_int_conversion`: + `reverse_bits`