Add some tests on adapted references with varargs and reflection

Also rename "varargAndDefaults" test directory to "adaptedReferences"

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

@@ -0,0 +1,9 @@
+// !LANGUAGE: +NewInference +FunctionReferenceWithDefaultValueAsOtherType
+
+fun foo(x: String, y: String = "K"): String = x + y
+
+fun call(f: (String) -> String, x: String): String = f(x)
+
+fun box(): String {
+    return call(::foo, "O")
+}