[release/6.0] Add cast when replacing promoted struct with field in lowering (#58951)

[release/6.0] Add cast when replacing promoted struct with field in lowering (#58951)

* Add cast when replacing promoted struct with field in lowering

We may need to sign/zero-extend when we do this replacement very late.
Normally this cast would be inserted in morph.

Fix #58373

* Add test

* Fix formatting

* Fix test cases

* Type returned-struct-as-primitive correctly for normalization

Retyping it to the type of the ret node is not right when reinterpreting
small structs as a type that needs to be normalized.

* Fix assertion

* Run jit-format

Co-authored-by: Jakob Botsch Nielsen <jakob.botsch.nielsen@gmail.com>