This changes `ControllerManager` to `Node`.
`Node` is created from a client where the VK lib is responsible for
creating all the things except the client (unless client is nil, then we
use the env client).
This should be a good replacement for node-cli. It offers a simpler
API. *It only works with leases enabled* since this seems always
desired, however an option could be added to disable if needed.
The intent of this is to provide a simpler way to get a vk node up and
running while also being extensible. We can slowly add options, but
they should be focussed on a use-case rather than trying to support
every possible scenario... in which case the user can just use the
controllers directly.
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