fix: enhance name splitting to handle "Lastname, Firstname" format

[enjeck]

Summary

If an ActiveDirectory provides user names in the "Lastname, Firstname" format, Nextcloud attempts to split this string internally, but it maps the values the wrong way around.
This becomes very obvious in the Contacts app, where the "First name" field is incorrectly populated with the user's last name including the comma (e.g., "Lastname,"), and the "Last name" field contains the user's actual first name

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

[Antreesy]

How does it cover cases like this?

• Jane Doe, MD
• Martin Luther King, Jr.
• Dr. Jane Doe

[Antreesy]

More or less that was implemented on Talk client side: https://github.com/nextcloud/spreed/pull/18682/changes

Might be an overkill, but basics to match would be:

• strip everything in braces
• strip common suffixes and prefixes, but no to mix with initials
• if there is a comma, check pattern for how many words are before comma:
  • a b, c - a supposed to be a first name
  • a, b c - b supposed to be a first name