Refactor metrics module to be agnostic of data source

[alrevuelta]

Refactors the metrics module to be agnostic from the data source, so that its peer information can be fetched either from rumor in the case of armiarma-client or via gRPC calls for the armiarma-server. This module should define all structs related to the information that we want to store for each peer and its operations.

The goal is to make it a reusable module, that can be used by both the client and the server. This will allow to access both the aggregated metrics and single crawler metrics with the same interface. It's also important to decouple it from the rest of the code, making it also easier to unit test.

Work in progress:

• [x] Remove unused code in metrics folder
• [x] Remove related code to peerstore.go and extra metrics. Same metrics can be achieved if needed but in a simpler manner.
• [x] Make gossip-metrics rumor agnostic.
• [x] Refactor Clients structs and make them more generic
• [x] Move all prometheus code into metrics control/actor/prometheus/start.go
• [x] Add unit tests
• [x] Move PollPeerMetadata and IP-API out of metrics.
• [x] Reimplement AnalyzeClientType
• [x] Move ping-metadata.go out of metrics as its not related.

[cortze]

Not sure if it was already in mind to implement a local database hosting the old PeerMetrics. we might be interested in adding a badger db which allows fast reading and writing, and key-value-version searches. What do you think?

[alrevuelta]

Thanks for the comments! One thing, were you checking the latest commit? I just see the diff between the first two ones. Perhaps you plan to review commit by commit?

Not sure if it was already in mind to implement a local database hosting the old PeerMetrics. we might be interested in adding a badger db which allows fast reading and writing, and key-value-version searches. What do you think?

Yep, thats an important feature. Let's move the discussions related to the db persistence to #18 since @kkhalil7 is working on that. I had in mind boltdb as its quite simple, also key-value and used by prysm software. However I don't have anything against badger-db.