ci/a618: Rebalance a618-limozeen jobs

Adjust job allocations and introduce nightly monitoring for zink tests due to recent changes in test farm resources.

1. Rebalance Jobs: Respond to the retirement of sc7180-trogdor-lazor-limozeen-cbg-2 by redistributing tasks to manage the increased job queue.

2. Adjust zink-tu-a618 tests: Halve the test volume on zink-tu-a618 following a reduction in a618-limozeen capacity at Collabora's farm.

3. Add zink-tu-a618-full job: Establish a nightly pipeline job to track zink test performance and stability.