Add a search bar to the `/groups/{pubid}/edit` page

[seanh]

Depends on https://github.com/hypothesis/h/issues/9133.

Add a search bar to the /groups/{pubid}/edit page.

This can be seen in the designs here: https://www.figma.com/design/jon1U01LGSLcx7PWtZ9TPZ/Hypothesis---Group-Management?node-id=2677-127&node-type=canvas&t=WbQZqgZOTMUcskEI-0