…te (which supports Vanilla and ZSA) - but for now zcash_primitives is not generalised itself and pinned to Vanilla only

…te (which supports Vanilla and ZSA) - but for now zcash_primitives is not generalised itself and pinned to Vanilla only

This PR updates `librustzcash` to accommodate the recent refactoring
changes in the `orchard` crate. The specific changes include:

- Renamed all references from `orchard_flavors` to `orchard_flavor` to
match the new module name.
- Updated the `OrchardDomain` trait references to `OrchardDomainCommon`
to reflect the trait renaming.
- Adjusted the `Bundle` structure to use the fixed `NoteValue` type for
the `burn` field, replacing the previous generic argument.
- Refactored associated code to align with the new structure and naming
conventions in the `orchard` crate.
- Switched from the `orchardzsa-backward-compatibility-0.8.0-ak` to
`orchardzsa-backward-compatibility-0.8.0` branch in `Cargo.toml` to use
the latest version of the `orchard` crate.

---------

Co-authored-by: Dmitry Demin <[email protected]>

)

This PR makes the following changes:
- reordering of the component fields in `read_action` and `write_action`
in issuance in order to make them spec compliant.
- It sets some of the constant values for NU7 in a way that is
consistent with the generated test vectors from the Python reference
implementation (See QED-it/zcash-test-vectors#22
for the changes to the Python reference implementation).
- Some changes are made to function names to reflect the shift from
preparing ZSAs for V7 rather than V6.
- There are changes to the tests to use the `zcash_unstable` flag in
order to cover both ZSA and vanilla Orchard behavior.
- The test vectors are also expanded to include both the V5 vectors, and
the V7 vectors (behind a `zcash_unstable` flag).

This PR updates the `zcash_primitives` crate to align with the recent
changes in the `sapling-crypto` crate, which was updated to sync with
the latest changes in `zcash_note_encryption`.

### Changes:
- Updated the usage of `enc_ciphertext` to call `.as_ref()` to match the
new return type.
- Adjusted the import of the `ENC_CIPHERTEXT_SIZE` constant to use the
definition from `sapling-crypto` instead of `zcash_note_encryption`, as
the constant has been moved to `sapling-crypto`.

Co-authored-by: Dmitry Demin <[email protected]>

This updates the test vectors to be of version 6 (as opposed to
version 7).

It also provides a new file for the V6 test vectors, an improvement to
having them in the same file but behind feature flags.

It provides a error for when the asset description string is not a UTF8
encoding.