Rollup merge of #87273 - fee1-dead:impl-const-impl-bounds, r=oli-obk

Recognize bounds on impls as const bounds

r? ```@oli-obk```

src/test/ui/rfc-2632-const-trait-impl/call-generic-in-impl.rs

@@ -0,0 +1,15 @@
+// check-pass
+#![feature(const_fn_trait_bound)]
+#![feature(const_trait_impl)]
+
+trait MyPartialEq {
+    fn eq(&self, other: &Self) -> bool;
+}
+
+impl<T: PartialEq> const MyPartialEq for T {
+    fn eq(&self, other: &Self) -> bool {
+        PartialEq::eq(self, other)
+    }
+}
+
+fn main() {}