Group dependabot updates for gradle test dependencies

[jmagman]

After #8048 I was expecting dependabot to update all packages given a particular dependency bump, but that doesn't seem to be happening. For example #8097 only updated shared_preferences_android.

So let's try adding groups to see if that does it. Group the obvious test dependencies together.

Part of flutter/flutter#148098

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/packages repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or this PR is exempt from CHANGELOG changes.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[jmagman]

This group name is arbitrary, it's not a special dependabot keyword.

[stuartmorgan]

For example #8097 only updated shared_preferences_android.

That appears to be the only package with that dependency. So it may still be working as expected?

[jmagman]

For example #8097 only updated shared_preferences_android.

That appears to be the only package with that dependency. So it may still be working as expected?

Hm, you're right, and I don't see any other new and open ones that would have updated multiple packages.
I'm going to close a few (trivial) old open dependabot PRs and see what it recreates on the next round. Moving this to draft.