[backport#16185 2/3] tests: Add a new functional test for gettransaction

Summary:
https://github.com/bitcoin/bitcoin/pull/16185/commits/b8b3f0435a2837d3897e9e232ef6ca839ce74eb8

Depends on D7370

Partial backport of Core PR16185

Test Plan:

test_runner.py wallet_basic

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7371