feat/746 - Updates for Ledger HW (shielded keys)

[jurevans]

Resolves #746

Also this implements a stepped process, so users can know what's happening on the ledger (now that there's 3 approvals instead of 1):

1. Transparent address & public key
2. Zip32 Viewing Key derivation
3. Zip32 Proof-Gen Key derivation

See #1458 from @mateuszjasiuk - We'll also need these changes.

• Update to latest @zondax/ledger-namada package (currently at 2.0.0)
• Remove HID transport (see: https://developers.ledger.com/docs/device-interaction/ledgerjs/integration/web-application/web-hid-usb - we should use either HID or USB, but not include support for both!). WebUSB seems to have the most support (supports older versions than WebHID), so we'll use that.
  • WebUSB
  • WebHID
• Updates to Ledger class in SDK
  • Methods for getViewingKey and getProofGenerationKey (split up getShieldedKeys so that we may turn these into steps, as they are separate approvals)
  • Update type returned for ViewingKey (now returns xfvk)
  • Before storing xfvk, convert to proper bech32m encoding (zvknam1)
• Store xfvk, ak and nsk
• It currently takes about 10 seconds to derive viewing key and proof-gen key (each!): We should notify the user what is happening, as there is not indication on Ledger when it is deriving these keys, they will only see each prompt after waiting about 10 seconds

TESTING

• Run yarn on this branch to get updated packages
• Install v2.0.2 of Ledger app (via https://hub.zondax.ch/namada for now) NOTE This will require that you are on the latest firmware, so update if needed!
• Import Ledger account

DESIGNS

Approval steps

SCREENSHOTS

Version detection (NOTE: 2.0.0 is the correct min-version, I just did this as a test since I am already upgraded to the latest Ledger app):

[jurevans]

was just simplifying here - we do not need to track the whole shielded account, only the payment address to display in confirmation