Rollup merge of #120587 - lukas-code:miri-tail-normalize, r=RalfJung

miri: normalize struct tail in ABI compat check

fixes #3282
extracted from rust-lang/rust#120354, see rust-lang/rust#120354 (comment) for context

r? ```@RalfJung```

tests/pass/issues/issue-miri-3282-struct-tail-normalize.rs

@@ -0,0 +1,20 @@
+// regression test for an ICE: https://github.com/rust-lang/miri/issues/3282
+
+trait Id {
+    type Assoc: ?Sized;
+}
+
+impl<T: ?Sized> Id for T {
+    type Assoc = T;
+}
+
+#[repr(transparent)]
+struct Foo<T: ?Sized> {
+    field: <T as Id>::Assoc,
+}
+
+fn main() {
+    let x = unsafe { std::mem::transmute::<fn(&str), fn(&Foo<str>)>(|_| ()) };
+    let foo: &Foo<str> = unsafe { &*("uwu" as *const str as *const Foo<str>) };
+    x(foo);
+}