Rollup merge of #150817 - cleanup-inline-const-pat-borrowck, r=lcnr

cleanup: remove borrowck handling for inline const patterns

rust-lang/rust#120390 added borrow-checking for inline const patterns; a type annotation was added to inline const patterns in the THIR to remember the `DefId` and args of the constants so they could be checked and constraints could be propagated to their parents. As of rust-lang/rust#138499 though, inline const patterns can't be borrow-checked due to a query cycle, and as of rust-lang/rust#149667, the type/`DefId`/args annotations on inline const patterns have been removed, so the borrowck code for them seems unused; this PR removes it.

In a hypothetical future where borrowck doesn't depend on exhaustiveness checking so `inline_const_pat` can be reinstated, I imagine we also won't be evaluating inline const patterns before borrowck. As such, we might be able to reuse the existing code for normal unevaluated inline const operands in [`TypeChecker::visit_operand`](https://github.com/rust-lang/rust/blob/32fe406b5e71afbb0d8b95280e50e67d1549224c/compiler/rustc_borrowck/src/type_check/mod.rs#L1720-L1749) (or at least we shouldn't need to encode inline const patterns' `DefId` and args in user type annotations if they appear directly in the MIR).

r? lcnr

Author: JonathanBrouwer