tech(alias): Create a container to handle aliased values

[pjechris]

⚽️ Description

Revamp the way aliases are handled inside the SDK: instead of relying on double Observable just create a wrapper (AliasContainer) and update its content everytime the alias changes. Rest of the SDK will then do the work! 🎉

🔨 Implementation details

• Create a new type, AliasContainer that represents a alias and its content (value)
• Store EntityNode<AliasContainer<T>> instances instead of complexe Observable<EntityNode<T>>
• Register aliases changes inside ObserverRegistry
• Because now aliases behave like any entity, AliasObserver is not needed anymore and we can also use EntityObserver for aliases