This adds a new workflow `update_kittest_snapshots.yml` that can be
triggered through the [kitdiff](https://github.com/rerun-io/kitdiff) ui
when viewing a ci artefact.
Also adds a link to kitdiff to view the pr changes to each commit (via
the preview build comment)
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
It seems like the thresholds are too low for all tests to pass when
snapshots are generated from windows / linux. We need a better solution
to this problem, but in the meantime this script should allow
contributors to update their snapshots by downloading them from the last
CI run.