Allow fake overrides and delegates to be impl for header declarations

Also fix a bug with matching supertype lists of header/impl classes

compiler/testData/diagnostics/tests/multiplatform/implDelegatedMember.kt

@@ -0,0 +1,19 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+header open class Foo {
+    open fun bar(): String
+}
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+
+interface Bar {
+    fun bar(): String
+}
+
+val bar: Bar
+    get() = null!!
+
+impl open class Foo : Bar by bar

compiler/testData/diagnostics/tests/multiplatform/implDelegatedMember.txt

@@ -0,0 +1,31 @@
+// -- Module: <m1-common> --
+package
+
+public open header class Foo {
+    public constructor Foo()
+    public open header fun bar(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+
+// -- Module: <m2-jvm> --
+package
+
+public val bar: Bar
+
+public interface Bar {
+    public abstract fun bar(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public open impl class Foo : Bar {
+    public constructor Foo()
+    public open override /*1*/ /*delegation*/ fun bar(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/multiplatform/implFakeOverride.kt

@@ -0,0 +1,16 @@
+// !LANGUAGE: +MultiPlatformProjects
+// MODULE: m1-common
+// FILE: common.kt
+
+header class Foo {
+    fun bar(): String
+}
+
+// MODULE: m2-jvm(m1-common)
+// FILE: jvm.kt
+
+open class Bar {
+    fun bar() = "bar"
+}
+
+impl class Foo : Bar()

compiler/testData/diagnostics/tests/multiplatform/implFakeOverride.txt

@@ -0,0 +1,30 @@
+// -- Module: <m1-common> --
+package
+
+public final header class Foo {
+    public constructor Foo()
+    public final header fun bar(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+
+// -- Module: <m2-jvm> --
+package
+
+public open class Bar {
+    public constructor Bar()
+    public final fun bar(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final impl class Foo : Bar {
+    public constructor Foo()
+    public final override /*1*/ /*fake_override*/ fun bar(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}