Auto merge of #66927 - RalfJung:engines-dont-panic, r=oli-obk

Auto merge of #66927 - RalfJung:engines-dont-panic, r=oli-obk

Miri core engine: use throw_ub instead of throw_panic

See https://github.com/rust-lang/rust/issues/66902 for context: panicking is not really an "interpreter error", but just part of a normal Rust execution. This is a first step towards removing the `InterpError::Panic` variant: the core Miri engine does not use it any more.

ConstProp and ConstEval still use it, though. This will be addressed in future PRs.

From what I can tell, all the error messages this removes are actually duplicates.

r? @oli-obk @wesleywiser