Add Miniscript support on the desktop app

[ben-kaufman]

We need to add support for Miniscript on the desktop app.

On the Desktop app side, we will need to integrate with async-hwi, since the normal HWI library does not support Miniscript.

On the mobile side, we will also need a few changes:

• We should make sure the user does wallet registration before signing or verifying address (I think at least for Ledger that'll be necessary).
• For Ledger, on wallet registration, the Desktop app will return an HMAC which is specific for the registered vault. The mobile app will need to save this HMAC, and send it to the desktop app in the verify address and sign tx commands. (Note that this will be needed also for non miniscript wallets with Ledger, but support for it on the desktop app side might come later).
• For all devices registration, the app should send a wallet name and the policy (policy will be used instead of the descriptorString, which should be empty in case the vault is miniscript), for sign tx and verify address, the app should also send the same wallet name and policy with the commands.

[ben-kaufman]

I think this belongs to Sprint 39 no? @cakesoft-utkarsh