Count OP_CHECKDATASIG and OP_CHECKDATASIGVERIFY as sigops when the proper flag is set.
As per title. Once the opcode activates, it needs to count as a sigops.
Depends on D1601
Test Plan: Added test cases.
Reviewers: #bitcoin_abc, schancel, jasonbcox
Reviewed By: #bitcoin_abc, schancel, jasonbcox
Subscribers: jasonbcox, teamcity
Differential Revision: https://reviews.bitcoinabc.org/D1605