Ingest and expose stacker/signer set event data
PR https://github.com/stacks-network/stacks-core/pull/4269 adds a new event /new_pox_anchor which exposes stacker/signer set data. We need to ingest these and will then be able to expose much of the (non-sBTC related) data requested at https://github.com/hirosystems/explorer/issues/1248
Somewhat blocked on https://github.com/hirosystems/stacks-blockchain-api/issues/1763 -- progress can be made, but integration tests for it require running against epoch3 which isn't yet stable
The initial ingestion and endpoints for this were implemented in https://github.com/hirosystems/stacks-blockchain-api/pull/1873. There are more detailed issues open tracking further work around this area: https://github.com/hirosystems/stacks-blockchain-api/issues/1953