Merge #15772: test: Properly log named args in authproxy

Summary:
fa078984c9 test: Properly log named args in authproxy (MarcoFalke)

Backport of Core PR15772

Test Plan:

./test/functional/wallet_balance.py --tracerpc

Just one example pulled from the output:
Pre-patch:

-23-> generatetoaddress []

Post-patch:

-23-> generatetoaddress {"nblocks": 1, "address": "mjTkW3DjgyZck4KbiRusZsqTgaYTxdSz6z", "maxtries": 1000000}

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8031