08fc6f6cfc3b06fd170452a766696d7b833113fa [rpc] refactor: consolidate sendmany and sendtoaddress code (Sjors Provoost)
Pull request description:
I consolidated code between these two RPC calls, since `sendtoaddress` is essentially `sendmany` with 1 destination.
Unless I overlooked something, the only behaviour change is that some `sendtoaddress` error codes changed from `-4` to `-6`. The release note mentions this.
Salvaged from #18201.
ACKs for top commit:
fjahr:
Code review ACK 08fc6f6cfc3b06fd170452a766696d7b833113fa
jonatack:
ACK 08fc6f6cfc3b06fd170452a766696d7b833113fa
meshcollider:
Code review & functional test run ACK 08fc6f6cfc3b06fd170452a766696d7b833113fa
Tree-SHA512: 7b66c52fa0444a4d02fc3f81d9c2a386794d447616026a30111eda35fb46510475eea6506a9ceda00bb4e0230ebb758da5d236b3ac05c954c044fa68a1e3e909
