Allow const patterns of matches to contain pattern types

[oli-obk]

Trying to pattern match on a type containing a pattern type will currently fail with an ICE

error: internal compiler error: compiler/rustc_mir_build/src/builder/matches/test.rs:459:18: invalid type for non-scalar compare: (u32) is 1..
  --> src/main.rs:22:5
   |
22 |     TWO => {}
   |     ^^^

because the compiler tries to generate a MIR BinOp(Eq) operation on a pattern type, which is not supported. While we could support that, there are side effects of allowing this (none that would compile, but the compiler would simultaneously think it could == pattern types and that it could not because PartialEq is not implemented. So instead I change the logic for pattern matching to transmute pattern types to their base type before comparing.

r? @BoxyUwU

cc #123646 @scottmcm @joshtriplett

[rustbot]

Some changes occurred in match lowering

cc @Nadrieril

[BoxyUwU]

leftover change from prev approach?

[BoxyUwU]

Can you add a comment explaining that we only support pattern types on the basic scalar types rn which all implement Copy so its fine to just unconditionally do a Operand::Copy here instead of the usual "is it copy mod regions" thing.