feat(settings): add shared Office admin section

[joshtrichards]

Summary

This changeset introduces a new shared Office admin settings section. It adds a canonical IIconSection for office so office-related apps can register their settings under a single umbrella section instead of each shipping their own separate section.

Encourages apps to stop defining app-specific section implementations and register their settings under office instead, similar to groupware, connected-apps, etc.

For example, if one has richdocuments + richdocumentscode installed, both register their own sections. This is confusing to the end-user since it adds to the "noise" at the top-level of the admin settings sections list plus they're both part of the overall "Office" setup (and the latter has very little contained in it anyhow).

Existing apps do not have to transition (but they should IMO) so there's no compatible problem introduced.

TODO

• ...

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI