[backport#15247] qa: Use wallet to retrieve raw transactions

Summary:
Merge #15247: qa: Use wallet to retrieve raw transactions

fa5278a419 qa: Use wallet to retrieve raw transactions (MarcoFalke)
fa2198328e qa: Style-only fixes in touched files (MarcoFalke)

Pull request description:

Instead of asking the coin database and block storage about a transaction, pull it directly from th$
This refactoring only makes sense in light of #15159.
<sub>This product may contain minor stylistic cleanups

Depends on D6062

This is a backport of Core PR15247

Test Plan:

./test_runner.py wallet_abandonconflict.py wallet_basic.py

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D6069