[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/vararg/intersectionOnVarargOverride.kt.txt

@@ -0,0 +1,63 @@
+abstract class A : Java1, Java2 {
+  constructor() /* primary */ {
+    super/*Java1*/()
+    /* <init>() */
+
+  }
+
+}
+
+class B : Java1, Java2 {
+  constructor() /* primary */ {
+    super/*Java1*/()
+    /* <init>() */
+
+  }
+
+  override fun foo(vararg a: String) {
+  }
+
+}
+
+abstract class C : Java2, KotlinInterface {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+}
+
+class D : Java2, KotlinInterface {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+  override fun foo(vararg a: Any) {
+  }
+
+  override fun foo(vararg a: String?) {
+  }
+
+}
+
+interface KotlinInterface {
+  abstract fun foo(vararg a: Any)
+
+}
+
+fun test(a: A, b: B, c: C, d: D) {
+  a.foo(a = [1, 2])
+  a.foo(a = ["1", "2"])
+  a.foo(a = [null])
+  b.foo(a = [1, 2])
+  b.foo(a = ["1", "2"])
+  b.foo(a = [null])
+  c.foo(a = [1, 2])
+  c.foo(a = ["1", "2"])
+  c.foo(a = [null])
+  d.foo(a = [1, 2])
+  d.foo(a = [null])
+}