[Chronik] Make TxId and the hashes serde serializable

Summary: This allows us to store TxIds and hashes in the DB.

Test Plan: cargo check -p bitcoinsuite-core

Reviewers: Fabien, #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15007