Format Groovy files in root Maven module with Spotless

[basil]

This PR formats Jenkinsfile and licenseCompleter.groovy, using a common Groovy configuration from the new shared-resources artifact. While the primary motivation behind this change is to make these files easier to read, the secondary motivation is that I intend to do some work on the Jenkinsfile in this repository soon, and since there is no compiler for that code it is helpful to have at least an AST parser to check over syntax before trying to run the code on a real Jenkins server.

Testing done

Ran mvn clean verify -DskipTests.

Proposed changelog entries

N/A

Proposed upgrade guidelines

N/A

Submitter checklist

• The Jira issue, if it exists, is well-described.
• The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples).
  • Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
• There is automated testing or an explanation as to why this change has no tests.
• New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadocs, as appropriate.
• New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO"), if applicable.
• New or substantially changed JavaScript is not defined inline and does not call eval to ease future introduction of Content Security Policy (CSP) directives (see documentation).
• For dependency updates, there are links to external changelogs and, if possible, full differentials.
• For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

@mention

Maintainer checklist

Before the changes are marked as ready-for-merge:

• There are at least two (2) approvals for the pull request and no outstanding requests for change.
• Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
• Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
• Proper changelog labels are set so that the changelog can be generated automatically.
• If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
• If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[NotMyFault]

/label ready-for-merge

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This PR is now ready for merge. We will merge it after ~24 hours if there is no negative feedback.
Please see the merge process documentation for more information about the merge process.
Thanks!

[basil]

Thanks for starting the merge process Alex. Since I have another PR that builds on top of this one and since this PR is fairly minor, I am going to expedite this change a little early so that I can make progress more quickly on the next PR that depends on this one without dealing with merge conflicts.

[MarkEWaite]

Caused JENKINS-71147 - cannot compile Jenkins core on aarch64 Linux, s390x Linux. Likely cannot compile core on ppc64le also.