Merge Piece Meta store codebase and boostd-data service behind a feature flag

[nonsense]

Given that the changeset at #573 is becoming increasingly larger and complex, we should release the Piece Meta store / boostd-data service feature behind a feature flag, so that we manage complexity of upcoming PRs and can continuously test the feature before marking it experimental and stable / GA.

Ultimately this is a step on the path to:

• refactor the data model and schema for deals on Boost and allow for data to be stored in an external database
• migrate all data from the DAGStore into the Piece Meta store
• refactor Boost into a stateless service, so that we can scale it horizontally

[jacobheun]

@nonsense this can be closed correct?