JVM: Mangle functions returning inline class values

Mangling suffix is base64-encoded MD5 of ":<returnTypeFQN>"

compiler/testData/codegen/box/inlineClasses/kt38680.kt

@@ -0,0 +1,13 @@
+// !LANGUAGE: +InlineClasses
+
+inline class IC(val s: String)
+
+interface IFoo<T> {
+    fun foo(x: T, s: String = "K"): String
+}
+
+class FooImpl : IFoo<IC> {
+    override fun foo(x: IC, s: String): String = x.s + s
+}
+
+fun box(): String = FooImpl().foo(IC("O"))