[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/basicVarargOverride.kt.txt

@@ -0,0 +1,81 @@
+class A : Java1 {
+  constructor() /* primary */ {
+    super/*Java1*/()
+    /* <init>() */
+
+  }
+
+}
+
+class B : Java1 {
+  constructor() /* primary */ {
+    super/*Java1*/()
+    /* <init>() */
+
+  }
+
+  override fun foo(vararg a: String?) {
+  }
+
+}
+
+abstract class C : Java2 {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+}
+
+class D : Java2 {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+  override fun foo(vararg a: Any) {
+  }
+
+}
+
+abstract class E : KotlinInterface2 {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+}
+
+class F : KotlinInterface2 {
+  constructor() /* primary */ {
+    super/*Any*/()
+    /* <init>() */
+
+  }
+
+  override fun foo(vararg a: Any) {
+  }
+
+}
+
+interface KotlinInterface {
+  abstract fun foo(vararg a: Any)
+
+}
+
+interface KotlinInterface2 : Java2 {
+}
+
+fun test(a: A, b: B, c: C, d: D, e: E, f: F) {
+  a.foo(a = ["", "1"])
+  a.foo(a = [null])
+  b.foo(a = ["", "1"])
+  b.foo(a = [null])
+  c.foo(a = ["", "1"])
+  d.foo(a = ["", "1"])
+  e.foo(a = ["", "1"])
+  f.foo(a = ["", "1"])
+}