Veritas, zone signing and proofs

[buffrr]

This PR:

1. Creates a new lib veritas enabling consumers to verify spaces in a stateless way using Merkle proofs.

2. Spaces will build and maintain a trust anchors file by default (can be disabled with --skip-anchors

3. A new /root-anchors.json endpoint and getrootanchors RPC method.

4. Space-cli now has signzone which creates a signed DNS packet bundled with a merkle proof for publishing.

5. Space-cli now has refereshanchor which refreshes bundled proofs

6. provespaceout and provespaceoutpoint RPC options to generate merkle proofs

7. Prefix crate names with spaces_ and rename node to client to more accurately reflect CSV (Client Side Validation)

8. Unifies signing operations to adopt the Nostr event format. Removes signmessage and replaces it with signevent. To sign a message, you could sign a Nostr note. For dns events, we use kind 871222 for now.

[horologger]

Don't forget to change the cargo build command node->client. Just looking at this now.