Add versioned signatures for Sapling transactions

[ConstanceBeguier]

Add SighashInfo (version and associated data) to

• Sapling binding signatures, and
• Sapling authorizing signatures

Update sapling_auth_digest by adding SighashInfo as defined in ZIP246

[PaulLaux]

approved with minor comments

[PaulLaux]

also,
Please remove #TODO comment in Transaction_v6.py:
assert have_orchard_zsa or not have_issuance #TODO: VA: Combine this with the above?

[PaulLaux]

combine both if's into one

[ConstanceBeguier]

I cannot combine both into one because the last line is into hasSapling loop but not into hasSigashInfo loop

[PaulLaux]

let's remove this param hasSighashInfo completly and replace with a runtime check for the class:

if isinstance(self, (TransactionV6)):

[PaulLaux]

all checks (x2)

[PaulLaux]

or tx.version_bytes() == NU7_TX_VERSION_BYTES: to be unified with below

[ConstanceBeguier]

Done

[PaulLaux]

Are all test files regenerated? I don't see new files for Sapling

[ConstanceBeguier]

Are all test files regenerated? I don't see new files for Sapling

Only transaction V6 is updated. So, only orchard_zsa_digests is updated.