KT-31908 Handle SAM conversion on vararg elements

compiler/testData/codegen/box/funInterface/funConversionInVararg.kt

@@ -0,0 +1,17 @@
+// !LANGUAGE: +NewInference +FunctionalInterfaceConversion +SamConversionPerArgument
+fun interface MyRunnable {
+    fun run()
+}
+
+fun box(): String {
+    var result = "failed"
+    val r = MyRunnable { result += "K" }
+    foo({ result = "O" }, r)
+    return result
+}
+
+fun foo(vararg rs: MyRunnable) {
+    for (r in rs) {
+        r.run()
+    }
+}