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
Part of T438