test: shift coverage from getunconfirmedbalance to getbalances

Summary:

Improve getbalances coverage in wallet_balance tests
and shift some getunconfirmedbalance calls to getbalances, as the former is
deprecated, while leaving essential coverage for it in test_balances().

Shift coverage from getunconfirmedbalance to getbalances in wallet_abandonconflict tests

Use getbalances in wallet_address_types tests

This is a backport of Core PR18451

Test Plan: test/functional/test_runner.py wallet*

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8927