Metrics for the dispatcher

[renan061]

📚 Context

We need to add metrics to the dispatcher. See #17.

📈 Subtasks

• [x] Implement a metrics library wrapping over Prometheus.
• [x] Define what metrics we are going to expose.
• [ ] Implement the metric signaling code.

[renan061]

We will start with these three metrics:

• cartesi_rollups_dispatcher_claims_sent_total
• cartesi_rollups_dispatcher_advance_inputs_sent_total
• cartesi_rollups_dispatcher_finish_epochs_sent_total