[chronik] Electrum: support prefixless addresses

Summary:
It guesses the prefix based on a predefined list.

Depends on D18121.

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/D18122