[chronik-client] Properly handle txs ordering in the test

Summary:
Unconfirmed txs are sorted by time first seen, then txid.
Confirmed txs are sorted by txid.
History txs are sorted by reverse time first seen, then reverse txid.

Let's not assume the time is the same in the test, because time first seen is not mockable. Instead we actually perform the appropriated sort.

Test Plan:

./contrib/teamcity/build-configurations.py chronik-client-integration-tests

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: PiRK

Differential Revision: https://reviews.bitcoinabc.org/D18084