make bip-39 view-only wallets capable of PSBT on android

[pony-montana]

Hi, I think would be good to make the android version capable to do psbt with bip-39 view only wallets.

EDIT:

A solution could be:

• Integrate an explicit way to populate the [derivation path] and [fingerprint] field when importing bip-39 view-only wallets. On desktop it is possible to do that using the console or importing some specially crafted json. On android, as far as I tried, it is not possible as android electrum lacks console and the "import wallet" possibility.

I think a GUI explicit solution in the wizard would be the best and it would expand electrum compatibility with bip-39 either on desktop and android.

If this solution wouldn't be considered well, a way to give power users a workaround is to integrate in the android version at least one of these functions, to make it "on pair" with desktop:

• console.
• import wallet from file (to import view-only wallet with populated fields from electrum desktop or from HW). This feature seems to me the less controversial to implement.

[ghost43]

This is not really related to the android/qml gui.

It should get solved as part of necessary wizard changes once we have #5715 / #5694.

I will close this now as I would prefer not to add temporary hacks just for this.