Support inline class values inside string templates through boxing

#KT-25626 Fixed
 #KT-25613 Open

compiler/testData/codegen/box/inlineClasses/inlineClassValuesInsideStrings.kt

@@ -0,0 +1,31 @@
+// !LANGUAGE: +InlineClasses
+// IGNORE_BACKEND: JVM_IR
+
+inline class Augmented(val x: Int) {
+    override fun toString(): String = (x + 1).toString()
+}
+
+inline class AsAny(val a: Any) {
+    override fun toString(): String = "AsAny: $a"
+}
+
+data class AugmentedAndAsAny(val a: Augmented, val b: AsAny)
+
+fun box(): String {
+    val a = Augmented(0)
+    val single = "$a"
+    if (single != "1") return "Fail 1: $single"
+
+    val asAny = AsAny(42)
+    val asAnyString = "$asAny"
+    if (asAnyString != "AsAny: 42") return "Fail 2: $asAnyString"
+
+    val b = Augmented(1)
+    val two = "$a and $b"
+    if (two != "1 and 2") return "Fail 3: $two"
+
+    val d = AugmentedAndAsAny(a, asAny)
+    if (d.toString() != "AugmentedAndAsAny(a=1, b=AsAny: 42)") return "Fail 4: $d"
+
+    return "OK"
+}