Rollup merge of #144016 - davidtwco:sized-hierarchy-temp-pseudo-revert, r=lcnr

trait_sel: `MetaSized` always holds temporarily

As a temporary measure while a proper fix for `tests/ui/sized-hierarchy/incomplete-inference-issue-143992.rs` is implemented, make `MetaSized` obligations always hold. In effect, temporarily reverting the `sized_hierarchy` feature. This is a small change that can be backported.

cc rust-lang/rust#143992
r? ```@lcnr```

Author: fmease