Add bulk editing to the `/groups/{pubid}/edit` page

[seanh]

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

Add bulk editing to the /groups/{pubid}/edit page, so the user can select multiple memberships at once or select all memberships and delete them all in one click

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

[seanh]

There's an issue with this when one of the selected members is the user themselves. Do we allow a user to remove multiple members, including themselves, in one click? Do we have to show a different warning dialog if one of the selected users is yourself? Do we make the user's own row not-selectable? But then is that confusing when the select-all button actually selects all rows but one? Related: https://github.com/hypothesis/h/issues/9135

I also think the utility of bulk editing is questionable:

I think it's unlikely that anyone is going to want to click the select-all box and remove all of the members of the group (including themselves?) at once: this would completely nuke the group. It might be better not to provide a UI that potentially allows users to do this accidentally.

When removing multiple but not all members from a group, I think bulk editing might not actually save many clicks. To remove three members from the group I would need to:

1. Click three times to select all three members
2. Click the Remove 3 members button to remove them

So four clicks total. Whereas without this feature, to remove three members I would need to:

1. Click the trash icon button next to each one of the three members

So it's actually fewer clicks without this feature!

This is not actually true because when removing members one-by-one the frontend currently shows a confirmation dialog for each member, so it would actually be six clicks. But still--I think the utility of bulk editing is questionable.