This PR improves the naming of variables to make them consistent with
the broader ZIPs conventions.
It also makes changes to the issuance key derivation and the terms used
for the various keys.
This makes the naming conventions for variables more consistent, largely with a view to using double backticks for terms that appear in the transaction format and datatype description tables.
These tables have also been reformatted to be consistent with other ZIPs in their rst form.
The `previously_finalized` set is renamed to `finalized_assets`, and this set now stores `AssetDigest` values rather than `AssetId` values for more compactness in the global state.
This details the changes to the transaction digest algorithm for the
ZSA protocol.
- A new branch is added for hashing the information in a transaction
related to issuance.
- Some branches are added and modified in the orchard_digest subtree to
account for the additional Asset Base value that needs to be hashed.
This rearranges and rewrites various sections of the ZIP to make it more in line with the suggestions in ZIP 0.
It also updates the Split Notes, Circuit Statement and Burn Mechanism sections with more information.
This covers the changes made to derive the issuance key independently of the Orchard key structure, using the techniques from [ZIP 32](https://zips.z.cash/zip-0032).
Vivek Arte
Antoine Rondelet
Daira-Emma Hopwood