[chronik] Electrum: Add more verbose fields to transaction.get

Summary: This makes the endpoint output closer to what the node returns.

Test Plan:

./test/functional/test_runner.py chronik_electrum_blockchain

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D18292