Rollup merge of #97077 - ouz-a:Optimize-backend, r=oli-obk

Simplify some code that depend on Deref

Now that we can assume #97025 works, it's safe to expect Deref is always in the first place of projections. With this, I was able to simplify some code that depended on Deref's place in projections. When we are able to move Derefer before `ElaborateDrops` successfully we will be able to optimize more places.

r? `@oli-obk`