Fixes for IR serialization plugin

- Do not insert typeParameters into IrConstructor;
- Set correct property symbol to IrField;

- Use upper bound as a class descriptor for type parameters.
This will allow to get upper bound's KClass in polymorphic serialization.
Fixes https://github.com/Kotlin/kotlinx.serialization/issues/490;

- Lazily add all serializer functions.
Fixes https://github.com/Kotlin/kotlinx.serialization/issues/502;

- Don't generate constructor invocation for abstract(sealed) classes deserializer.
Such code is incorrect anyway (you can't create an instance of abstract class) and causes problems in devirtualization when exporting Native libraries.

plugins/kotlin-serialization/kotlin-serialization-compiler/testData/codegen/Basic.ir.txt

@@ -188,10 +188,8 @@ public final class ListOfUsers$$serializer : java/lang/Object, kotlinx/serializa
           ALOAD (4)
           ALOAD (3)
           INVOKEINTERFACE (kotlinx/serialization/CompositeEncoder, endStructure, (Lkotlinx/serialization/SerialDescriptor;)V)
-        LABEL (L2)
-        LINENUMBER (13)
           RETURN
-        LABEL (L3)
+        LABEL (L2)
     }
 
     public void serialize(kotlinx.serialization.Encoder encoder, java.lang.Object obj) {
@@ -493,10 +491,8 @@ public final class OptionalUser$$serializer : java/lang/Object, kotlinx/serializ
           ALOAD (4)
           ALOAD (3)
           INVOKEINTERFACE (kotlinx/serialization/CompositeEncoder, endStructure, (Lkotlinx/serialization/SerialDescriptor;)V)
-        LABEL (L7)
-        LINENUMBER (10)
           RETURN
-        LABEL (L8)
+        LABEL (L7)
     }
 
     public void serialize(kotlinx.serialization.Encoder encoder, java.lang.Object obj) {
@@ -840,10 +836,8 @@ public final class User$$serializer : java/lang/Object, kotlinx/serialization/in
           ALOAD (4)
           ALOAD (3)
           INVOKEINTERFACE (kotlinx/serialization/CompositeEncoder, endStructure, (Lkotlinx/serialization/SerialDescriptor;)V)
-        LABEL (L2)
-        LINENUMBER (7)
           RETURN
-        LABEL (L3)
+        LABEL (L2)
     }
 
     public void serialize(kotlinx.serialization.Encoder encoder, java.lang.Object obj) {