lister.tests: Explicit required scheduler task-type needed for each lister

This installs the expected output task-type the lister outputs in the scheduler.

This was partially done on some lister but not all. This aligns everything.

Now every lister has a conftest with the required fixture. And every lister is called after its name lister_{gnu,launchpad, ...}

Hopefully this clarifies the tests. It did for me when i was tracking down the build failures.

Test Plan

tox happy

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Migrated from D4386 (view on Phabricator)