Rollup merge of #139108 - Nadrieril:simplify-expandedconstant, r=oli-obk

Simplify `thir::PatKind::ExpandedConstant`

I made it a bit less ad-hoc. In particular, I removed `is_inline: bool` that was just caching the output of `tcx.def_kind(def_id)`. This makes inline consts a tiny bit less special in patterns.

r? `@oli-obk`

cc `@Zalathar`

Author: Zalathar