Add support for deb822 apt sources format

[deosrc]

The decision on format to use is determined by the visual_studio_code_use_deb822_format variable. I'm not aware of a way to auto-detect the preferred format.

I've tried to keep this consistent with the style of other areas, so the forking logic (i.e. decision of deb822 or oneline format) uses include_tasks to "skipped" tasks. This means the original apt source setup needed extracting to a separate file.

Rather than re-use the apt key setup, I've jsut used the built-in functionality of the deb822_repository task. The only difference I believe would be the filename.

I'm not sure how to write molecule tests so haven't been able to add those, but have tested using check mode for both, and run mode for deb822.

Resolves #259

[CLAassistant]

All committers have signed the CLA.

[MaKaNu]

#264 is working on the same topic. There are still a few quirks if migrating from one to the other.