Auto merge of #113758 - cjgillot:move-dse, r=JakobDegen,oli-obk

Turn copy into moves during DSE.

Dead store elimination computes whether removing a direct store to an unborrowed place is allowed.
Where removing a store is allowed, writing `uninit` is too.

This means that we can use this pass to transform `copy` operands into `move` operands. This is only interesting in call terminators, so we only handle those.

Special care is taken for the `use_both(_1, _1)` case:
- moving the second argument is ok, as `_1` is not live after the call;
- moving the first argument is not, as the second argument reads `_1`.

Fixes #75993
Fixes rust-lang/rust#108068

r? `@RalfJung`
cc `@JakobDegen`

Author: bors