Exhaustively handle expressions in patterns

[oli-obk]

We currently have this invariant in HIR that a PatKind::Lit or a PatKind::Range only contains

• ExprKind::Lit
• ExprKind::UnOp(Neg, ExprKind::Lit)
• ExprKind::Path
• ExprKind::ConstBlock

So I made PatKind::Lit and PatKind::Range stop containing Expr, and instead created a PatLit type whose kind enum only contains those variants.

The only place code got more complicated was in clippy, as it couldn't share as much anymore with Expr handling

It may be interesting on merging ExprKind::{Path,Lit,ConstBlock} in the future and using the same PatLit type (under a new name).

Then it should also be easier to eliminate any and all UnOp(Neg, Lit) | Lit matching that we have across the compiler. Some day we should fold the negation into the literal itself and just store it on the numeric literals

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[rustbot]

HIR ty lowering was modified

cc @fmease

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred in match checking

cc @Nadrieril

[rustbot]

HIR ty lowering was modified

cc @fmease

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred in match checking

cc @Nadrieril

[compiler-errors]

@rustbot author

[oli-obk]

I removed the PatKind::Path removal from this PR. I think it should be done, but I'm doing it as a follow-up PR in #134248

@rustbot ready