[backport#15930] rpc: Deprecate getunconfirmedbalance and getwalletinfo balances

Summary:
https://github.com/bitcoin/bitcoin/pull/15930/commits/facfb4111d14a3b06c46690a2cca7ca91cea8a96

Depends on D6446

Concludes backport of Core PR15930

Test Plan:

ninja
./src/bitcoind -regtest -daemon
./src/bitcoin-cli -regtest getunconfirmedbalance help
./src/bitcoin-cli -regtest getwalletinfo help

Check if it looks good

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6447