Rollup merge of #137617 - BoxyUwU:generic_const_parameter_types, r=lcnr

Introduce `feature(generic_const_parameter_types)`

Allows to define const generic parameters whose type depends on other generic parameters, e.g. `Foo<const N: usize, const ARR: [u8; N]>;`

Wasn't going to implement for this for a while until we could implement it with `bad_inference.rs` resolved but apparently the project simd folks would like to be able to use this for some intrinsics and the inference issue isn't really a huge problem there aiui. (cc ``@workingjubilee`` )

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -1189,9 +1189,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         let span = obligation.cause.span;
 
         let mut diag = match ty.kind() {
-            _ if ty.has_param() => {
-                span_bug!(span, "const param tys cannot mention other generic parameters");
-            }
             ty::Float(_) => {
                 struct_span_code_err!(
                     self.dcx(),