Anchor wants the `notify` function to run only in certain cases - so the `spawn_notifier` function is unsuitable for us.
Anchor uses it's own `notify` function, which then calls `notifier_service::notify` (in most circumstances). To enable that, `notify` needs to be `pub`.
We would like to reuse the `notifier` and `latency_service` in Anchor. To make this possible, this PR moves these from `validator_client` to `validator_services` and makes them use the new `ValidatorStore` trait is used so that the code can be reused in Anchor.
