After the tinyformat switch sprintf() family functions support passing
actual std::string objects.
Remove unnecessary c_str calls (236 of them) in logging and formatting.
Split bitcoinrpc up into
- rpcserver: bitcoind RPC server
- rpcclient: bitcoin-cli RPC client
- rpcprotocol: shared common HTTP/JSON-RPC protocol code
One step towards making bitcoin-cli independent from the rest
of the code, and thus a smaller executable that doesn't have to
be linked against leveldb.
This commit only does code movement, there are no functional changes.