Campaign edit/close/delete buttons should be disabled while Campaign is processing

Created by: mrnugget

We should disable the Edit/Close/Delete buttons on the Campaign details page while the Campaign is still processing and changesets are being created on the codehost.

We already don't allow updating the campaign while it's processing and in https://github.com/sourcegraph/sourcegraph/pull/8240 I added the checks for Close/Delete on the backend side.