Sqlite backend

[buffrr]

This a large PR as it changes the wallet persistence and touches many parts of the codebase. Changes include:

1. Switch to the sqlite backend for better stability
2. Store additional metadata about a transaction such as which tx is a bid, open, transfer ... etc
3. Watch the mempool for bid replacements to free up locked funds without having to wait for confirmation
4. listspaces now shows which spaces have been outbid
5. Use a batched version of bdk to handle issues with conflicting bid transactions
6. Update bdk to the most recent stable version
7. Graceful RPC retries
8. Create extra bidouts to save on tx fees
9. Add wallet sync checks to make sure spaces and wallet tips are up to date
10. Several other bug fixes and stability imporvements.

Fixes #53
Fixes #54
Fixes #45