[backport#16689 1/2] MOVEONLY : move RPC wallets helpers to TransactionDescriptionString

Summary:
https://github.com/bitcoin/bitcoin/pull/16689/commits/353010849185cda53c97da1f5089565dccf6f16a

Partial backport of Core PR16689

Test Plan:

ninja
bitcoin-cli help listtransactions|listsinceblock|gettransaction

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7384