Feature request: ability to verify transparent Zcash addresses too

[A6230]

As of v1.8.0, we're only able to verify unified address for shielded transactions on the Keystone device.

It would also be great to be able to verify transparent zcash addresses too, as many wallets currently don't support sending to shielded / unified addresses. Hence, we're relying on 'hot' software wallets to safely derive these, if users want to transfer funds across.

Thanks for the great work on the app!