IR: 'fun interface' support

compiler/testData/ir/irText/expressions/funInterface/basicFunInterfaceConversion.kt

@@ -0,0 +1,9 @@
+// !LANGUAGE: +NewInference +FunctionalInterfaceConversion +SamConversionPerArgument +SamConversionForKotlinFunctions
+
+fun interface Foo {
+    fun invoke(): String
+}
+
+fun foo(f: Foo) = f.invoke()
+
+fun test() = foo { "OK" }