[Part 1 of 3] Split signrawtransaction into wallet and non-wallet

Summary:
Splits signrwatransaction into a wallet version (signrawtransactionwithwallet) and
non-wallet version (signrawtransactionwithkey). signrawtransaction 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 (partial backport of commit 1e79c05)

Note: in order to not break the tests, the signrawtransaction deprecation will be backported in a later diff, once all the tests are updated to the new RPC.

Part of T438

Test Plan:

make check
./test/functional/test_runner.py signrawtransactions txn_clone abc-high_prioriy_transaction

Reviewers: #bitcoin_abc, jasonbcox, deadalnix

Reviewed By: #bitcoin_abc, jasonbcox, deadalnix

Subscribers: markblundeberg, deadalnix, jasonbcox, teamcity

Differential Revision: https://reviews.bitcoinabc.org/D2007