Rollup merge of #143927 - oli-obk:const-dyn-trait-hir-ty, r=fmease

Preserve constness in trait objects up to hir ty lowering

r? ``@compiler-errors``

While we don't support `dyn const Trait`, we can at least also inform the user that `const Trait` is only legal for `#[const_trait] trait Trait {}`

Author: samueltardieu