The word "segwit" refers to segwit v0 and taproot but currently we have
`segwit_signature_hash` that is version specific (segwit v0).
- Rename `segwit_encode_signing_data_to` to
`segwit_v0_encode_signing_data_to`
- Add `p2wpkh_signature_hash` and `p2wsh_signature_hash` functions
We keep the single encode function because the error handling is better
that way.
While we are at it test the bip-143 test vectors against all the
sighash types of wrapped p2wsh.