[electrum][trezor] 1-click install of the eCash logo as a homescreen

Summary: This adds a new menu to the Trezor screen to install the eCash logo as the device background in a single click.

Test Plan:
Install the eCash homescreen on all the Trezor devices.
Checked it works on the Linux Appimage.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Subscribers: Mengerian, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17579