Rollup of 8 pull requests
Successful merges:
- #136542 ([`compiletest`-related cleanups 4/7] Make the distinction between root build directory vs test suite specific build directory in compiletest less confusing)
- #136579 (Fix UB in ThinVec::flat_map_in_place)
- #136688 (require trait impls to have matching const stabilities as the traits)
- #136846 (Make `AssocOp` more like `ExprKind`)
- #137304 (add `IntoBounds::intersect` and `RangeBounds::is_empty`)
- #137455 (Reuse machinery from `tail_expr_drop_order` for `if_let_rescope`)
- #137480 (Return unexpected termination error instead of panicing in `Thread::join`)
- #137694 (Spruce up `AttributeKind` docs)
r? `@ghost`
`@rustbot` modify labels: rollup