enh(systemtags): Add accessible system tags form

[Pytal]

• For [BITV] Make admin collaborative tags markup accessible #41208

Summary

	Screenshot
Before
After

To Do

• Tests

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)

[JuliaKirschenheuter]

😱 would need time to review

[ShGKme]

Works fine.

But from a11y perspective, I'm not sure that this is clear when this form is at the same time create and edit form, especially when searching a tag to edit is a part of the form.