Reorganized VKTree services and implemented startup consumption of sequencer arguments for workers

[rpanic]

Closes #207

Description in the issue

Enhanced the FlowTaskWorker to accept three different types of tasks:
UnpreparingTask: Tasks that don't implement a prepare() method, therefore they don't have to wait for registration to get initialized - important because we need the CircuitCompilerTask before we have working worker registration
AbstractStartupTask: Tasks that are used for startup of workers: Mainly the WorkerRegistrationTask
Task: All normal tasks that wait for registration to be completed before preparing and registering for tasks

[ejMina226]

Looks good.

[ejMina226]

@rpanic From a high-level, how did you get around the issue of the worker processes not having access to the VKTreeService?

[rpanic]

@ejMina226
Two-fold: The first thing I did was instead of accessing the VKTreeService in the BlockProver, which is executed by a task, I add the VK and the tree witness as a task payload and through that, I use them in the BlockProver as a traditional program arguments / witness.
The second thing is how the blockprover has access to the tree root, which has to be baked into the circuit at compile time. This is done via a extra step that happens when the worker gets started, which is the "worker registration". I outlined that in more detail in the linked issue