Additional DLC commands

[Schellbach]

Commands to implement:
request_adjudication
get_adjudication_status
get_public_key
get_announcement
get_attestation

Notes:

• EscrowAgent trait requires the Oracle trait https://docs.rs/dlc-manager/0.4.0/dlc_manager/trait.Oracle.html
• The DLC needs to handle nip4 response