Rollup merge of #90066 - yaahc:thinbox, r=joshtriplett

Rollup merge of #90066 - yaahc:thinbox, r=joshtriplett

Add new ThinBox type for 1 stack pointer wide heap allocated trait objects

**Zulip Thread**: https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/ThinBox

Based on https://github.com/matthieu-m/rfc2580/blob/b58d1d3cba0d4b5e859d3617ea2d0943aaa31329/examples/thin.rs

Tracking Issue: https://github.com/rust-lang/rust/issues/92791

Usage Trial: https://github.com/yaahc/pgx/pull/1/files

## TODO

- [x] make sure to test with #[repr(align(1024))] structs etc