[wireformat] Use signatures instead of qualified names when possible

[toth-istvan-zoltan]

As of now:

• wire formats contain fully qualified class names for polymorphic formats even when the data is primitive
• WireFormatRegistry also uses fully qualified names for primitive types

object WireFormatRegistry : Registry<WireFormat<*>>() {
    init {
        val n = WireFormatTypeArgument<Any>(PolymorphicWireFormat, true)
        
        set("kotlin.Any", PolymorphicWireFormat)

        set("kotlin.Byte", ByteWireFormat)
        set("kotlin.Short", ShortWireFormat)
        set("kotlin.Int", IntWireFormat)

This feels like a waste when we actually have short signatures already.

Investigate if the conversion of these long names into signatures is feasible.