FE: add tests to reproduce KT-56720

compiler/testData/diagnostics/tests/override/manyImplFromOneJavaInterfaceWithDelegation.fir.kt

@@ -0,0 +1,19 @@
+// FILE: A.java
+
+public interface A {
+    default void foo() {}
+}
+
+// FILE: B.java
+
+public interface B extends A
+
+// FILE: C.java
+
+public interface C extends A
+
+// FILE: test.kt
+
+class Adapter : B, C
+
+<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class D<!>(val adapter: Adapter) : B by adapter, C by adapter

compiler/testData/diagnostics/tests/override/manyImplFromOneJavaInterfaceWithDelegation.kt

@@ -0,0 +1,19 @@
+// FILE: A.java
+
+public interface A {
+    default void foo() {}
+}
+
+// FILE: B.java
+
+public interface B extends A
+
+// FILE: C.java
+
+public interface C extends A
+
+// FILE: test.kt
+
+class Adapter : B, C
+
+class D(val adapter: Adapter) : B by adapter, C by adapter

compiler/testData/diagnostics/tests/override/manyImplFromOneKotlinInterfaceWithDelegation.kt

@@ -0,0 +1,20 @@
+// FIR_IDENTICAL
+// FILE: A.kt
+
+interface A {
+    fun foo() {}
+}
+
+// FILE: B.kt
+
+interface B : A
+
+// FILE: C.kt
+
+interface C : A
+
+// FILE: test.kt
+
+class Adapter : B, C
+
+<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class D<!>(val adapter: Adapter) : B by adapter, C by adapter