[backport#14689] Require a public key to be retrieved when signing a P2PKH input

Summary:
If we do not have the public key for a P2PKH input, we should not
continue to attempt to sign for it.

Depends on D6028

This is a backport of Core PR14689

Test Plan:

cmake .. -GNinja -DENABLE_WERROR=ON
ninja check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6029