std: Stabilize the rest of Any/BoxAny

This commit stabilizes the following APIs:

* `TypeId::of` - now that it has an `Any` bound it's ready to be stable.
* `Box<Any>::downcast` - now that an inherent impl on `Box<Any>` as well as
  `Box<Any+Send>` is allowed the `BoxAny` trait is removed in favor of these
  inherent methods.

This is a breaking change due to the removal of the `BoxAny` trait, but
consumers can simply remove imports to fix crates.

[breaking-change]

0 files changed, 0 insertions, 0 deletions