Add RX OTA flash for frsky X10s & X12s.

[isjfk]

Fixes #2147

Summary of changes:
The OTA flash code are basically copied from stdlcd, rewrite UI part based on the new implementation for color screens.

The UI part cost me some time. My finding is to close dialogs & menus programmatically, they needs to be deleteLater() in stack order, from latest widget to older widget. If the order is wrong the UI will crash immediately. After fix the order of deleteLater(), the UI works fine.

I run several tests in my X10s, click no and yes, flash by OTA several times. Seems working well in my device. It should also work in X12s, but I don't have a device to test.

[ParkerEde]

I have now tried this pull request.
I select "Flash by int. OTA", then it comes waiting for Rx. Now I plug the battery on the Rx (which is correctly bound and works) but unfortunately nothing happens. The receiver is not recognized and thus the flash process does not start. I test with X10SExpress and Archer R8pro

[ParkerEde]

After I re-registered and bound the Rx again, the recognition of the Rx at power on worked and the flash process runs.

@pfeerick I would appreciate it if we could still include this pull request in version 2.9. Thanks a lot

[ParkerEde]

I have now flashed more Archer R6 RX. All of them worked right away. Good job, thank you @isjfk

[pfeerick]

That should be fine... really just need confirmation testing (since it's mainly just adding the missing UI bits) and you've provided that 😁

[isjfk]

@ParkerEde My pleasure! Thanks for your verification.

[isjfk]

I have now tried this pull request. I select "Flash by int. OTA", then it comes waiting for Rx. Now I plug the battery on the Rx (which is correctly bound and works) but unfortunately nothing happens. The receiver is not recognized and thus the flash process does not start. I test with X10SExpress and Archer R8pro

Seems if the model was upgraded from OpenTX, the receiver still work but it cannot be bind again or OTA flashed. It never shown up in the list. I have my X-Lite upgrade yesterday, although it's not a color screen by exactly same issue happen.

Probably because the Owner ID was changed during the upgrade. My Owner ID changed to some random chars that cannot be displayed correctly. Have to reset the Owner ID in TX, delete the receiver, register & bind again to make it OTA flash-able (just like you did).