Auto merge of #106938 - GuillaumeGomez:normalize-projection-field-ty, r=oli-obk

Add missing normalization for union fields types

Overshadows rust-lang/rust#106808.
From the experiment rust-lang/rust#103985.

In short, it allows to use projections as a type for union's fields.

cc `@compiler-errors`
r? `@oli-obk`

Author: bors