[2.x] chore(core): open confirm box before deleting permission scope

[DavideIadeluca]

Fixes #0000
Accidentally hitting the delete button for removing a scope

Changes proposed in this pull request:
Minor Quality of Life Improvement for Community Managers / Admins. Opens a Confirmation Box before a permission scope is deleted.

From past experiences "deleting" that scope doesn't actually irreversibly delete the configured permissions — unclear if this is intended behaviour or a bug. But erring on the side of caution I still choose a terminology which still somewhat suggests that the action is destructive

Reviewers should focus on:

Screenshot

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

Required changes:

• Related documentation PR: (Remove if irrelevant)