[Chronik] Use struct init for QueryTxs instead of new

Summary: While using new is fine, once we add more fields to QueryTxs using positional parameters becomes less readable, so we use the clearer struct init.

Test Plan: ninja check-crates

Reviewers: Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D13693