Disallow using addresses in createmultisig

Summary:
Make createmultisig only accept public keys with the old functionality
marked as deprecated.

Splits _createmultisig_redeemscript into two functions, one for
getting public keys from UniValue and one for getting addresses
from UniValue and then their respective public keys. The one for
retrieving address's public keys is located in rpcwallet.cpp

Adds a test to deprecated_rpc.py for testing the deprecation.

Update the tests to give only public keys to createmultisig.

Depends on D1967 and D2001

Backport of Core PR11415

Test Plan:

make VERBOSE=1 check && ./test/functional/test_runner.py

Reviewers: #bitcoin_abc, schancel, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien, teamcity

Differential Revision: https://reviews.bitcoinabc.org/D2002