Move querying scheduled rewards to individual modules

[bajtos]

See the discussion in #259:

It's the module's decision whether to use Meridian. ethers might even run in Zinnia, since for this we don't need to sign messages - or we could just use the jsonrpc endpoint directly - then we only need fetch. I think for this we need a way for Zinnia modules to log metrics.

### Tasks
- [ ] https://github.com/filecoin-station/zinnia/issues/421
- [ ] Release new Zinnia version and bring it to Station Core
- [ ] Update SPARK to use this new API
- [ ] Release new SPARK version and bring it to Station Core
- [ ] Rework Station Core to use this new metric provided by `zinniad`

[bajtos]

@juliangruber is this something we should consider for the DARC workstream or are you ok to duplicate the current code in Station Core to query scheduled rewards for another module?

[juliangruber]

Good question, let's decide as we work on the implementation