Add some tests on adapted references with varargs and reflection

Also rename "varargAndDefaults" test directory to "adaptedReferences"

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

@@ -0,0 +1,13 @@
+// !LANGUAGE: +NewInference
+// IGNORE_BACKEND_FIR: JVM_IR
+// WITH_RUNTIME
+// KJS_WITH_FULL_RUNTIME
+
+inline fun foo(mkString: (Char, Char) -> String): String =
+        mkString('O','K')
+
+fun bar (vararg xs: Char) =
+        String(xs)
+
+fun box(): String = foo(::bar)
+// -> { a, b -> bar(a, b) }