feat(core,chain): implement Display, FromStr, FromSql and ToSql for BlockId

[luisschwab]

This PR implements Display, FromStr for BlockId, and FromSql and ToSql for Impl<BlockId>, needed to persist the wallet's birthday as a BlockId (height + hash).

Changelog notice

• Implement Display and FromStr for BlockId
• Implement FromSql and ToSql for Impl<BlockId>

[evanlinjin]

ntACK fd9d558

[oleonardolima]

Concept ACK

It looks good, though I want to test it with the bdk_wallet companion PR before fully ACK'ing it.

[oleonardolima]

Also, the PR description is missing the CHANGELOG info.

[oleonardolima]

@luisschwab If you are looking forward to have this on 0.23.3 you'd need to either change the target branch to release/chain-0.23.x or open another backport PR alongside this one.

[luisschwab]

@oleonardolima I'll make a backport PR once this is merged on master.

[ValuedMammal]

It's not obvious that BlockId would have a FromStr impl, or that it would be implemented this way. I assume you can always persist a BlockId as two separate columns for the height and block hash.

[luisschwab]

t's not obvious that BlockId would have a FromStr impl, or that it would be implemented this way.

Well, since this our type we get to define how it's implemented. But perhaps it would be cleaner to do different rows for height and hash. I'll update this soon with this approach.

[luisschwab]

This is not needed anymore, since these conversions already exist for u32 and BlockHash.