Handle @Serializable classes that implement interfaces by delegation

by filtering out delegated properties that end up in irClass.properties() list

Fixes https://github.com/Kotlin/kotlinx.serialization/issues/2157

plugins/kotlinx-serialization/testData/boxIr/delegatedInterface.kt

@@ -0,0 +1,23 @@
+// TARGET_BACKEND: JVM_IR
+
+// WITH_STDLIB
+
+import kotlinx.serialization.*
+import kotlinx.serialization.descriptors.*
+import kotlinx.serialization.encoding.*
+import kotlinx.serialization.json.*
+
+@Serializable()
+class Dto(
+    val data: Map<Int, Int>
+) : Map<Int, Int> by data
+
+fun box(): String {
+    val dto = Dto(mapOf(1 to 2))
+    val s = Json.encodeToString(dto)
+    if (s != """{"data":{"1":2}}""") return s
+    val d = Json.decodeFromString<Dto>(s)
+    if (d.size != 1) return "Delegation to Map failed"
+    if (d.data != dto.data) return "Equals failed ${d.data}"
+    return "OK"
+}