Add tests for KT-52745

compiler/testData/codegen/box/delegation/sealedClass.kt

@@ -0,0 +1,11 @@
+// TARGET_BACKEND: JVM_IR
+// IGNORE_BACKEND_FIR: JVM_IR
+// WITH_STDLIB
+
+sealed class A : CharSequence {
+    data class B(val c: CharSequence) : A(), CharSequence by c
+}
+
+fun box(): String {
+    return A.B("OK").c.toString()
+}