Rollup merge of #156749 - cyrgani:unbox-full, r=Kivooeo,fmease

remove `box_patterns`

This PR removes the old feature `box_patterns`, tracked in https://github.com/rust-lang/rust/issues/29641. As explained in https://github.com/rust-lang/rust/issues/29641#issuecomment-1399430625, this feature will not be stabilized since `deref_patterns` (https://github.com/rust-lang/rust/issues/87121) is a better and more general version of this feature.

It was not possible to remove this feature until recently since the compiler itself still depended on this feature. This was changed with https://github.com/rust-lang/compiler-team/issues/984.

This PR currently breaks crates that rely on box patterns using the incorrect pre-expansion feature gating (see https://github.com/rust-lang/rust/issues/154045 for more details). Therefore, this needs a crater run.

Closes https://github.com/rust-lang/rust/issues/29641.
Closes https://github.com/rust-lang/rust/issues/105099.
Closes https://github.com/rust-lang/rust/issues/156110.