[Updater] Incorporate our first pass at grouped updates as an experiment we can ship

[brrygrdn]

This branch supersedes our original spike in #6663

Having established and shipped the "operation" pattern as a way to separate out the code paths for specific types of Dependabot::Job objects to avoid a lot of low-level branching, we can now package our experimental spike into a code structure we can safely ship without risking an impact on production jobs.

This PR introduces the Dependabot:: Updater::Operations::GroupUpdateAllVersions class which applies to all fresh, Version Updates which have a Dependabot::Experiment flag enabled.

This code is currently very lightly tested to confirm that it behaves identically to the existing adapter for a simple unit test case. I plan to add some smoke tests to demonstrate the correct grouping behaviour as a guard against regressions on this basic walking skeleton, but there is a job to be done in fleshing out the tests properly as a follow up.

[abdulapopoola]

any concerns with casing?

[brrygrdn]

I think it's ok at this point as we are using Dependabot::Dependency objects and the name should be normalised, plus this is currently replicating existing behaviour that hasn't been DRY'd out yet.

Case checking is something we have a few inconsistencies on though, so it's a good spot.

[brrygrdn]

I think we should probably remove shuffling within groups and instead shuffle the groups when we have more than one, but for now I think shuffling has the benefit that it might flush out issues compiling changes together if we run them in a random order - if we made this deterministic now it could result in false confidence.

[jakecoffman]

LGTM