[FIR] Don't remove subsumed members from intersection overrides's overriddens

This fixes a bunch of missing overridden symbols in IR.
This is also required for fixing KT-59921 in the following commit
where we need to keep all overridden symbols of intersection overrides
so that we can enhance them properly.

#KT-57300 Fixed
#KT-57299 Fixed
#KT-59921
#KT-57300
#KT-62788
#KT-64271
#KT-64382

compiler/testData/diagnostics/tests/override/clashesOnInheritance/intersectionReturnTypeMismatchSubsumed.kt

@@ -0,0 +1,41 @@
+// FIR_IDENTICAL
+
+// FILE: test.kt
+
+// We inherit getReturnType
+// from CallableDescriptor with return type String? and
+// from ClassConstructorDescriptorImpl with return type String
+// but because ClassConstructorDescriptorImpl.getReturnType subsumes CallableDescriptor.getReturnType, we don't report RETURN_TYPE_MISMATCH_ON_INHERITANCE.
+class DeserializedClassConstructorDescriptor : CallableDescriptor, ClassConstructorDescriptorImpl()
+
+// FILE: ClassConstructorDescriptorImpl.java
+
+// IJ reports an inspection warning
+// "Non-annotated method 'getReturnType' from 'FunctionDescriptorImpl' implements non-null method from 'ConstructorDescriptor'"
+// which is the underlying issue.
+public class ClassConstructorDescriptorImpl extends FunctionDescriptorImpl implements ConstructorDescriptor {}
+
+// FILE: FunctionDescriptorImpl.java
+public abstract class FunctionDescriptorImpl implements CallableDescriptor {
+    @Override
+    public String getReturnType() {
+        return null;
+    }
+}
+
+// FILE: ConstructorDescriptor.java
+import org.jetbrains.annotations.NotNull;
+
+public interface ConstructorDescriptor extends CallableDescriptor {
+    @NotNull
+    @Override
+    String getReturnType();
+}
+
+// FILE: CallableDescriptor.java
+import org.jetbrains.annotations.Nullable;
+
+public interface CallableDescriptor {
+    @Nullable
+    String getReturnType();
+}