Extract logic of builtins package fragment provider creation

This allows to drop the compile dependency of module 'descriptors' on
'deserialization', breaking the circular dependency between them

core/reflection.jvm/reflection.pro

@@ -14,6 +14,7 @@
 -keep class kotlin.reflect.jvm.internal.ReflectionFactoryImpl { public protected *; }
 
 -keep class * implements kotlin.reflect.jvm.internal.impl.resolve.ExternalOverridabilityCondition { public protected *; }
+-keep class * implements kotlin.reflect.jvm.internal.impl.builtins.BuiltInsLoader { public protected *; }
 
 -keepclassmembers enum * {
     public static **[] values();