When checking overrides, compare methods structurally

Because they may come from different copies of the same class from different modules

compiler/testData/diagnostics/tests/multimodule/duplicateSuper/sameSuperTrait.kt

@@ -0,0 +1,26 @@
+// MODULE: m1
+// FILE: x.kt
+package p
+
+public trait Base {
+    public fun foo() {}
+}
+
+public trait A : Base
+
+// MODULE: m2
+// FILE: x.kt
+package p
+
+public trait Base {
+    public fun foo() {}
+}
+
+public trait B : Base
+
+// MODULE: m3(m1, m2)
+// FILE: x.kt
+
+import p.*
+
+class Foo: A, B