[FIR] Allow declarations to override parts of non-trivial intersection

A class can inherit two declarations that are compatible from the
overridability standpoint and are therefore combined to a non-trivial
intersection.
At the same time, the class can declare a member declaration that
only overrides one of the intersection's members.
In this case, we break up the intersection and only add the overridden
parts to the declared member's direct overridden list.

If the class doesn't override the intersection, it exists as
intersection override, like before.

#KT-65487 Fixed

compiler/testData/codegen/box/javaInterop/immutableName.kt

@@ -0,0 +1,50 @@
+// TARGET_BACKEND: JVM
+// FILE: Base.java
+import org.jetbrains.annotations.NotNull;
+
+public interface Base {
+    Base foo(@NotNull String name);
+}
+
+// FILE: Derived.java
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public interface Derived extends Base {
+    @Override
+    @NotNull Derived foo(@Nullable String name);
+}
+
+// FILE: Impl.kt
+abstract class Impl : Base {
+    override fun foo(name: String): Base = this
+}
+
+// FILE: test.kt
+abstract class ImplDerived : Impl(), Derived {
+    abstract override fun foo(name: String?): Derived
+}
+
+abstract class DerivedImpl : Derived, Impl() {
+    abstract override fun foo(name: String?): Derived
+}
+
+fun box(): String {
+    val x1: ImplDerived = object : ImplDerived() {
+        override fun foo(name: String?): Derived = this
+    }
+    x1.foo("")
+    (x1 as Base).foo("")
+    (x1 as Derived).foo("")
+    (x1 as Impl).foo("")
+
+    val x2: DerivedImpl = object : DerivedImpl() {
+        override fun foo(name: String?): Derived = this
+    }
+    x2.foo("")
+    (x2 as Base).foo("")
+    (x2 as Derived).foo("")
+    (x2 as Impl).foo("")
+
+    return "OK"
+}