feat: add basic actor model

[Keith-CY]

This PR adds the actor model in a basic format for future development, an actor should have

• ref: reference to the actor;
• static method call/cast: send call/cast request to the message queue;
• instance method call/cast: wrapped static method call/cast;
• handleCall/handleCast: unified API to handle messages, and the messages will be delegated to user-defined business methods.

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Only actor is the key module implemented in this PR so it's covered by unit tests,
message-queue will be replaced with redis stream
and registry will be replaced with inversify so they are not covered by tests.

Besides, an example of how to use actors is added in src/examples/app

Ref: #4

[Keith-CY]

The most basic actor model is added for other components to interact, and an example of how the model should run is added in this PR, please have a review @PainterPuppets @felicityin @yanguoyu

[felicityin]

Does a example of communication between two actors need to be added?

[Keith-CY]

Does a example of communication between two actors need to be added?

The example in the PR shows how actors communicate with each other, the root actor requests its child to increment its state by one and gets a response saying the child one has updated its state.

> handle call request from root with symbol Symbol(one)
> /root: increment 1
> handle cast request from child_one with symbol Symbol(done)
> task is done

[felicityin]

Does a example of communication between two actors need to be added?

The example in the PR shows how actors communicate with each other, the root actor requests its child to increment its state by one and gets a response saying the child one has updated its state.

> handle call request from root with symbol Symbol(one)
> /root: increment 1
> handle cast request from child_one with symbol Symbol(done)
> task is done

I see it.

[Keith-CY]

Please have a review @PainterPuppets

[PainterPuppets]

The main idea delivered by the actor model is Divide-and-Conquer. If a heavy task is assigned to actor_a, the task would be split into sub-tasks and delegated to actor_a's child actors, recursively, until sub-tasks are small enough to be handled in one piece.

Is this part of the documentation implemented in another pr?

The current code does not seem to describe the behavior between parents and children

[Keith-CY]

The main idea delivered by the actor model is Divide-and-Conquer. If a heavy task is assigned to actor_a, the task would be split into sub-tasks and delegated to actor_a's child actors, recursively, until sub-tasks are small enough to be handled in one piece.

Is this part of the documentation implemented in another pr?

The current code does not seem to describe the behavior between parents and children

How to model users' business logic depends on their goals and kuai won't tell users how to split their tasks.

But one target of kuai is to help users to divide their big task into small tasks easily and suitable for cell model so some paradigms are adopted in kuai and expected to prevail in dapps built on kuai. Once these paradigms prevades, interoperability among dapps would increase.