feat: move `nodeData` to the ledger

[mudler]

Problem

Currently the nodeData is stored into the node's DHT which is transient and not guaranteed to always be accessible.

Proposed solution

As now we have a ledger implementation ( #380 ) we want to re-use that to store the nodeData information about the nodes instead of using DHT to make sure the data is consistently available to all nodes ( especially relevant in sight of #496 )

Acceptance criteria

• [ ] nodeData is accessible in the ledger
• [ ] DHT is not used to store nodeData

[mudler]

From an initial investigation on the current state of the code:

• Everything starts 'here' https://github.com/masa-finance/masa-oracle/blob/6dae3fe5c4aca9b6a1540b89a3399da34f84f87b/pkg/oracle_node_listener.go#L45 where we take from the NodeTracker all the nodeData that we want to ... broadcast to all the node.
• Everything that comes from the NodeTracker, for example, even when each node decides to cleanup, it gets published to all the nodes again to process and get picked up: https://github.com/masa-finance/masa-oracle/blob/6dae3fe5c4aca9b6a1540b89a3399da34f84f87b/pkg/pubsub/node_event_tracker.go#L458
• There is no real "current" nodeData state in the DHT. By de-facto every node gets his understanding of all the nodeData state by "accident", just because it is listening to as many things as it can via the node tracker. So basically everything is stored in the memory of the workers (https://github.com/masa-finance/masa-oracle/blob/main/pkg/pubsub/safe_map.go ) , and when needed (e.g. to search who distributes the work) we query the nodeTracker (for instance, here we get all the node data https://github.com/masa-finance/masa-oracle/blob/6dae3fe5c4aca9b6a1540b89a3399da34f84f87b/pkg/pubsub/node_event_tracker.go#L228 , but we rely on the fact that nodeTracker updated that map by receiving the events in the pubsub of the nodes

---

also, on a side node for the blockchain work - looks like even if it's a struct that is subscribed ( https://github.com/masa-finance/masa-oracle/blob/6dae3fe5c4aca9b6a1540b89a3399da34f84f87b/pkg/subscriptions.go#L19 ) , there is a single channel for the blockchain which is package-scoped: https://github.com/masa-finance/masa-oracle/blob/6dae3fe5c4aca9b6a1540b89a3399da34f84f87b/pkg/oracle_node.go#L345 so it is acting actually as a singleton