Complete PR14796 by cleaning up some old functions and names

Summary:
Finish PR14796 by removing and/or renaming old functions in
rpc/util.

Renaming done with sed "s/ToStringWithArgs/ToString/g" <files>

Depends on D5710, D5712, D5713, D5714. D5716, D5717, D5720, D5722, D5725, D5732

Test Plan:

mkdir master
mkdir patched

On master:

ninja
./bitcoind
./bitcoin-cli help > RPCs
./getrpchelps.sh RPCs master

On the patched branch:

ninja
./bitcoind
./getrpchelps.sh RPCs patched
./checkrpc.sh RPCs master patched finisheddiff

Verify there is no finisheddiff.

Scripts:

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5726