Renamed exclude file and set spotbugs default to medium

[StefanSpieker]

Renamed exclude file and set spotbugs default to medium. With this it is easier to switch the core to medium, you can just comment the line in the pom.

Proposed changelog entries

• N/A

Proposed upgrade guidelines

N/A

Submitter checklist

• (If applicable) Jira issue is well described
• Changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developer, depending on the change). Examples
  • Fill-in the Proposed changelog entries section only if there are breaking changes or other changes which may require extra steps from users during the upgrade
• Appropriate autotests or explanation to why this change has no tests
• For dependency updates: links to external changelogs and, if possible, full diffs

Desired reviewers

@mention

Maintainer checklist

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

• There are at least 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 does not block the change
• Changelog entries in the PR title and/or Proposed changelog entries are correct
• Proper changelog labels are set so that the changelog can be generated automatically
• If the change needs additional upgrade steps from users, upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the PR title. (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).

[oleg-nenashev]

Will it require extending the excludes file before the merge? I'd guess so. There was huge work to cleanup the codebase (thanks to everyone!) but I'd guess there are still some unfixed issues

[StefanSpieker]

I kept Medium for core. We still have a long road to go. But I think like that it is easier to work on the issues. You cannot forget to build the parent when you change the settings.
I also plan to involve a couple of colleagues during Hacktoberfest ;-)
So hopefully we will get closer to the goal...

[basil]

Thanks! I applied some fixups; I hope you don't mind. (If you do, let me know and I'll apply such fixups to a downstream PR in the future.)

[timja]

This PR is now ready for merge, after ~24 hours, we will merge it if there's no negative feedback.

Thanks!