Auto merge of #144847 - Randl:const-ord, r=oli-obk

Constify Eq, Ord, PartialOrd

Adds `#[const_trait]` and impls for `Eq`, `Ord`, `PartialOrd`. Impl for some other traits (e.g., slices and arrays) are blocked mainly on const closures (rust-lang/rust#106003).
For TypeId Ord we need const pointer comparison (rust-lang/rust#53020)
Tracking issue rust-lang/rust#143800

Author: bors