Create context on subscribers

[CrochetFeve0251]

Is your feature request related to a problem? Please describe.
Contexts are a great way in WP Rocket to decide whenever a callback is gonna execute or not.

Describe the solution you'd like
We would need that context into launchpad.

However, when adding them to Launchpad, we would like them to be instantiated apart from the subscriber.
That way we would be able to save save memory by just instantiating the context and bail out if without instantiating the subscriber if we don't need that logic.

Also, to simplify the logic to add a context and prevent repetitive code, we should be using annotations @context for that on the class or the method definition.

Priority should go on the method context if two contexts are registered.

Finally, for the context itself, to prevent any heavy constraints, it should just be a method or a class with php invoke method and without parameters.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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