JVM_IR: Fix Inline CallableReferences with Varargs

- Added tests to demonstrate broken behaviour: the interaction of inline
  functions and callable references with varargs and defaults in various
  combinations.
- Refactored InlineCallableReferencesToLambdaPhase to look like and use
  some of the infrastructure from CallableReferenceLowering.
- Lifted some of this infrastructure out to be broadly reusable.

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

@@ -0,0 +1,12 @@
+// !LANGUAGE: +NewInference
+// WITH_RUNTIME
+// IGNORE_BACKEND: JS, JS_IR
+
+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) }