Removed activation logic for OP_REVERSEBYTES to pretend it was always enabled
Activation logic is now unnecessary, assuming this code doesn't travel back in time.
This change removes the scriptflag SCRIPT_ENABLE_OP_REVERSEBYTES and all the places it gets activated.
Also entirely removes the activation tests.
Reviewers: deadalnix, O1 Bitcoin ABC, #bitcoin_abc, jasonbcox
Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox
Differential Revision: https://reviews.bitcoinabc.org/D6173