Rollup merge of #125968 - BoxyUwU:shrink_ty_expr, r=oli-obk

Store the types of `ty::Expr` arguments in the `ty::Expr`

Part of #125958

In attempting to remove the `ty` field on `Const` it will become necessary to store the `Ty<'tcx>` inside of `Expr<'tcx>`. In order to do this without blowing up the size of `ConstKind`, we start storing the type/const args as `GenericArgs`

r? `@oli-obk`

compiler/rustc_middle/src/ty/mod.rs

@@ -87,7 +87,7 @@ pub use self::closure::{
     CAPTURE_STRUCT_LOCAL,
 };
 pub use self::consts::{
-    Const, ConstData, ConstInt, ConstKind, Expr, ScalarInt, UnevaluatedConst, ValTree,
+    Const, ConstData, ConstInt, ConstKind, Expr, ExprKind, ScalarInt, UnevaluatedConst, ValTree,
 };
 pub use self::context::{
     tls, CtxtInterners, CurrentGcx, DeducedParamAttrs, Feed, FreeRegionInfo, GlobalCtxt, Lift,