BM-848: Add top level metrics

[capossele]

This PR adds top level metrics for

• IDs of requests that expired in [from, to)
• IDs of requests that expired in [from, to) for a given client
• Count of requests submitted in [from, to)
• Total count of all submitted requests
• Count of requests submitted in [from, to) from a specific client
• Total submitted requests by a specific client
• Count of fulfillments in [from, to)
• Total count of all fulfillments
• Count of fulfillments in [from, to) for a given client
• Total fulfillments for a specific client
• Count of fulfillments in [from, to) by a specific prover
• Total fulfillments by a specific prover
• Count of locked requests in [from, to) by a specific prover
• Total locked requests by a specific prover
• Count of slashed events in [from, to)
• Total count of all slashed events
• Count of slashed events in [from, to) by a specific prover
• Total slashed events by a specific prover
• Ratio of fulfilled ÷ locked requests in [from, to) for a prover
• Overall fulfilled ÷ locked ratio for a prover
• Ratio of fulfilled ÷ submitted requests in [from, to) for a client
• Overall fulfilled ÷ submitted ratio for a client

TODO

• Create lambdas for pushing metrics into Cloudwatch, maybe in a separate PR?