[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/sequenceMapIntersectionOverrideKJJ.kt

@@ -0,0 +1,28 @@
+// TARGET_BACKEND: JVM
+// JDK_KIND: FULL_JDK_21
+// WITH_STDLIB
+// SEPARATE_SIGNATURE_DUMP_FOR_K2
+// ^ ISSUE: KT-65667, KT-63914
+
+// FILE: 1.kt
+import java.util.*
+import kotlin.collections.HashMap
+
+abstract class A : HashMap<Int, Int>(), SequencedMap<Int, Int>
+
+class B : HashMap<Int, Int>(), SequencedMap<Int, Int> {
+    override fun reversed(): SequencedMap<Int, Int> {
+        return null!!
+    }
+}
+
+fun test(a: A, b: B){
+    a.size
+    a.putLast(null, 1)
+    a.putLast(2, null)
+    a.firstEntry()
+    a.lastEntry()
+    a.reversed()
+
+    b.reversed()
+}