555 refactor event system

[BartolomeyKant]

closes #555

Two main changes in this PR:

• Event System - now it uses centralized EventSystem object to manage all events. To define an event Event<void(args...)> object must be created and initialize with EventSystem& or any EventContext type. Each registered event obtain a key, each Subscription stores pointer to event system, key to registered event and pointer to assigned handler which is used later to unsubscribe.
• ApiProtocol - now every Api class must be derived from DeclareApi CRTP class and provide templated ApiList consteval function intended to be invoked with Api as template parameter. ApiList must return TypeList of RegMethod<MessageId, pointer to memeber function>. This is just an interface. To make client implementation call ClientMethod<&Api::Method>(args...) from that Method. To make server implementation, just do what you must to do in that Method. For client implementations messages are built without allocations - all messages temporary stored in generic storage with specified capacity - PacketList, suitable to store any message from that Api class.