change(devops): Reduce number of dependabot PRs

[teor2345]

Motivation

We're getting a lot of dependabot PRs, but some of them don't have a meaningful amount of changes. Others need to be grouped to pass CI.

Close #6547

Specifications

https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#groups

Complex Code or Requirements

We can update the groups later if they turn out not to work.

Solution

• Only check for dependency updates weekly on Mondays, rather than daily (some dependencies update multiple times per week)
• Group Rust dependency updates that usually happen together
• Reduce the maximum number of open PRs to 2 * (reviewers - 1), because often someone is away or busy

Testing

• add a validate dependabot step to our existing action lint job

Review

Let's try this and see how it goes?

Reviewer Checklist

• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

Follow Up Work

Gustavo (or someone else) might want to group related GitHub Actions dependency updates, but I'm not sure what those groups should be.

[upbqdn]

Looks great. Thanks for creating the groups.

[teor2345]

@Mergifyio update

[mergify]

update

✅ Branch has been successfully updated

[upbqdn]

lol

[teor2345]

lol

I think I tried to fix this in PR #7158, some of the auto-label settings are too much 🤣