Auto merge of #109357 - saethlin:inline-as-deref, r=thomcc

Add #[inline] to as_deref

While working on rust-lang/rust#109247 I found an `as_deref` call in the compiler that should have been inlined. This fixes the missing inlining (but doesn't address the perf issues I was chasing).

r? `@thomcc`

Author: bors