Fixes screenshot generator to work for generating all languages at once

[kdmukai]

Description

Running the screenshot generator for all languages would succeed on the first language, but then throw an exception when trying to restart a Toast thread. Beside that, other issues occurred due to how the first run through changes the Controller state and does not reset it for the next language's run.

The visual diff here is hard to digest, but the changes are actually very minor. The Controller setup and the list of target Views (screenshot_sections) are just wrapped into their own method that gets called for each language to ensure a clean state and no already-instantiated / already-running Toasts.

Sig type and script type are explicitly set in Settings, otherwise the related selection Views during xpub export won't render (the first test run sets each to a single option so a naive follow-up run will cause those Views to auto-skip themselves since there are no choices to make).

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This pull request is categorized as a:

• Bug fix

Checklist

• I’ve run pytest and made sure all unit tests pass before sumbitting the PR

If you modified or added functionality/workflow, did you add new unit tests?

• N/A

I have tested this PR on the following platforms/os:

• Raspberry Pi OS Manual Build

[jdlcdl]

Thank you 🙏