Access Trezor without connect.trezor.io

[CodeSandwich]

Describe the bug
To sign a transaction with Trezor, MetaMask opens https://connect.trezor.io/8/popup.html. This causes some issues:

• We're dependent on a 3rd party explicit consent to access our own private keys
• The downtimes of connect.trezor.io are frequent, which blocks access to funds and often makes MetaMask go into a limbo state requiring plugin restart

Steps to reproduce

1. Sign a transaction with Trezor

Expected behavior

MetaMask talks to Trezor locally, without requirement of online 3rd party services.

Browser details (please complete the following information):

• OS: any
• Hardware Wallet: Trezor One 1.9.4
• Browser: any (Chrome / Firefox)
• MetaMask Version: 9.2.0