[Test] KT-61360: add tests for the IrFakeOverrideBuilder

Add tests for fake overrides with focus on java interoperability

Co-authored-by: Aleksandra Arsenteva <aleksandra.arsenteva@jetbrains.com>

compiler/testData/ir/irText/fakeOverrides/java21/sequenceSetIntersectionOverrideKJJ.fir.kt.txt

@@ -0,0 +1,37 @@
+abstract class A : HashSet<Int>, SequencedSet<Int> {
+  constructor() /* primary */ {
+    super/*HashSet*/<Int>()
+    /* <init>() */
+
+  }
+
+  override fun spliterator(): Spliterator<Int> {
+    return CHECK_NOT_NULL<Nothing>(arg0 = null)
+  }
+
+}
+
+class B : HashSet<Int>, SequencedSet<Int> {
+  constructor() /* primary */ {
+    super/*HashSet*/<Int>()
+    /* <init>() */
+
+  }
+
+  override fun reversed(): SequencedSet<Int> {
+    return CHECK_NOT_NULL<Nothing>(arg0 = null)
+  }
+
+  override fun spliterator(): Spliterator<Int> {
+    return CHECK_NOT_NULL<Nothing>(arg0 = null)
+  }
+
+}
+
+fun test(a: A, b: B) {
+  a.<get-size>() /*~> Unit */
+  a.addFirst(p0 = null)
+  a.reversed() /*~> Unit */
+  b.reversed() /*~> Unit */
+  b.addFirst(p0 = 1)
+}