Remove TX_WITNESS_V0_SCRIPTHASH and TX_WITNESS_V0_KEYHASH

Summary: These are SegWit standard output. I initially kept them around for extension blocks, but it's getting in the way to get the anti replay feature in, so it goes.

Test Plan:

make check

Reviewers: freetrader, #bitcoin_abc

Reviewed By: freetrader, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D57