Enable Spotless formatting for Groovy files

[wborn]

Description

This enables GrEclipse formatting for Groovy files as part of the Spotless configuration.
The second commit applies Spotless formatting to the Groovy files.

Merge

The two commits should preferably remain separate:

1. Enable Spotless formatting for Groovy files — functional/configuration changes required to enable formatting.
2. Format Groovy files — formatting-only changes.

To preserve this separation, the PR should preferably be rebased/merged with the merge queue temporarily disabled rather than squashed.

After merging, the resulting SHA of the Format Groovy files commit can be added to .git-blame-ignore-revs, so the repository-wide formatting changes do not interfere with git blame.

Similar to openremote/openremote#3215

Checklist

• 1. Acceptance criteria of the linked issue(s) are met
• 2. Tests are written and all tests pass
• 3. Changes are manually tested by you and the reviewer
• 4. Documentation is written or updated