add support for Keystone account to the Receive tab

[true-jared]

• as a user I can switch between Zashi and Keystone wallet by tapping on the Zashi/Keystone dropdown and selecting the wallet in the bottom sheet

• if the user selects Keystone in the bottom sheet, they will see the addresses associated with the Keystone wallet (shielded in blue, transparent in grey)

• the screen retains the current interactions for both wallets:

  • Copy: copies the wallet address
  • QR Code: displays the QR code with the address embedded (design for Keystone)
  • Request ZEC: a user can create a payment request for the address