These types were previously part of the `zcash_primitives` crate and are
being included here to provide a migration path for when these types are
removed from `zcash_primitives`.
The structure of the `incrementalmerkletree` and `bridgetree` types has
not historically been stable, and as such it is not appropriate to
automatically derive serialization for these types.
The transitive dependency we have on `unarray` is forcing this update.
Also, update CI actions to eliminate dependencies on the unmaintained
`actions-rs` Rust CI tools.
Kris Nuttycombe