[Nakamoto] Signer details per cycle

[zone117x]

The API should calculate total stx/slots per Stacker/signer and make it available in an endpoint.

The current signer reward set events from the stacks-node only show signer-key<->stx relationships which isn't helpful to the end user.

We should show totals for pools and solo stackers, and show delegate info per pool. This requires scanning through historical pox4 events, and should probably be a materialized view which is calculated when receiving a pox anchor block.

[zone117x]

This is partially blocked by the state of stacks-node next branch. It cannot boot past 1 pox cycle into epoch3, so much of the data we need to implement this against isn't available.