Support Unit/V types in string-concat indy calls

unitComponent.kt test fails with JVM target 9+

compiler/testData/codegen/bytecodeText/stringOperations/concatDynamicUnit.kt

@@ -0,0 +1,28 @@
+// JVM_TARGET: 9
+data class A(val x: Unit)
+
+fun test(): Unit {}
+
+interface B<T> {
+    fun test() : T {
+        return null!!
+    }
+}
+
+class Foo : B<Unit> {
+
+}
+
+fun box(): String {
+    val a = A(Unit)
+
+    val test = "Test ${a.component1()} ${test()} ${Foo().test()}"
+    return "OK"
+}
+// one in data class `toString` and one in `box` method
+// 2 INVOKEDYNAMIC makeConcatWithConstants
+// 1 makeConcatWithConstants\(Lkotlin/Unit;\)
+// 1 makeConcatWithConstants\(Lkotlin/Unit;Lkotlin/Unit;Lkotlin/Unit;\)
+// 0 append
+// 0 stringPlus
+