[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/generics/genericMethodOverrideOnKJK.kt.txt

@@ -0,0 +1,83 @@
+abstract class A : Java2 {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+}
+
+class B : A {
+  constructor() /* primary */ {
+    super/*A*/()
+    /* <init>() */
+
+  }
+
+  override fun <T : Any?> bar(): T {
+    return CHECK_NOT_NULL<Nothing>(arg0 = null)
+  }
+
+  override fun <T : Any?> foo(a: T) {
+  }
+
+}
+
+class C : Java1 {
+  constructor() /* primary */ {
+    super/*Java1*/()
+    /* <init>() */
+
+  }
+
+}
+
+class D : Java1 {
+  constructor() /* primary */ {
+    super/*Java1*/()
+    /* <init>() */
+
+  }
+
+  override fun <T : Any?> bar(): T {
+    return CHECK_NOT_NULL<Nothing>(arg0 = null)
+  }
+
+  override fun <T : Any?> foo(a: T) {
+  }
+
+}
+
+interface KotlinInterface {
+  abstract fun <T : Any?> bar(): T
+
+  abstract fun <T : Any?> foo(a: T)
+
+}
+
+fun test(a: A, b: B, c: C, d: D) {
+  val k: Int = a.bar<Int>()
+  val k3: Any = a.bar<Any>()
+  a.foo<Int>(a = 1)
+  a.foo<Nothing?>(a = null)
+  a.foo<Int?>(a = null)
+  a.foo<List<Nothing?>>(a = listOf<Nothing?>(element = null))
+  val k5: Int? = b.bar<Int?>()
+  val k6: Any = b.bar<Any>()
+  b.foo<Int>(a = 1)
+  b.foo<Nothing?>(a = null)
+  b.foo<Int?>(a = null)
+  b.foo<List<Nothing?>>(a = listOf<Nothing?>(element = null))
+  val k7: Int? = c.bar<@FlexibleNullability Int?>()
+  val k8: Any = c.bar<@FlexibleNullability Any?>() /*!! Any */
+  c.foo<Int>(a = 1)
+  c.foo<Nothing?>(a = null)
+  c.foo<@FlexibleNullability Int?>(a = null)
+  c.foo<List<Nothing?>>(a = listOf<Nothing?>(element = null))
+  val k9: Int? = d.bar<Int?>()
+  val k10: Any = d.bar<Any>()
+  d.foo<Int>(a = 1)
+  d.foo<Nothing?>(a = null)
+  d.foo<Int?>(a = null)
+  d.foo<List<Nothing?>>(a = listOf<Nothing?>(element = null))
+}