Splits signrwatransaction into a wallet version (signrawtransactionwithwallet) and
non-wallet version (signrawtransactionwithkey). signrawtransaction is marked as DEPRECATED
and will call the right signrawtransaction* command as per the parameters in order to
maintain compatibility.
Updated signrawtransactions test to use new RPCs
Backport 1/3 of core PR10579
Depends on D1967, D2184 and D2214
Part of T438