[Chronik] Add Default derive to ffi structs in chronik-bridge

Summary: Having a default derive makes it much easier to write tests for these structs. Also sort the derives alphabetically while we're at it.

Test Plan: ninja check-crates

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D13498