Add some tests on adapted references with varargs and reflection

Also rename "varargAndDefaults" test directory to "adaptedReferences"

compiler/testData/codegen/box/callableReference/adaptedReferences/reflectionForVarargAsArray.kt

@@ -0,0 +1,22 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+
+import kotlin.reflect.KCallable
+
+private fun check(label: String, fn: Any) {
+    if (fn !is KCallable<*>) {
+        throw AssertionError("$label is not KCallable, ${fn::class.java.simpleName}")
+    }
+}
+
+fun checkVarargAsArray(label: String, fn: (IntArray) -> C) = check(label, fn)
+
+fun withVarargs(vararg xs: Int): C = C(*xs)
+class C(vararg xs: Int)
+
+fun box(): String {
+    checkVarargAsArray("::withVarargs", ::withVarargs)
+    checkVarargAsArray("::C", ::C)
+
+    return "OK"
+}