Support rqlite as a data store backend

[williamdes]

Ref: #634

This will close my etcd implementation that got limited by blob support: #742

See:

• https://rqlite.io/

Goals: provide a backend to store everything I need to store

• Data store
  • read
  • write
  • delete
• Blob store
• Full-text store
• Lookup store

https://stalw.art/docs/get-started

Since https://github.com/tomvoet/rqlite-rs/releases/tag/v0.5.0 it can be used to store blobs

Testing: STORE=rqlite cargo test store_tests --no-default-features --features=rqlite -- --nocapture

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