Fix incorrect CMS layout widths when bulk editing

[kinglozzer]

Description

The edit form is missing the necessary CSS class to ensure its width is consistent with other CMS sections.

Before:

After:

Manual testing steps

Bulk edit something. My edit form includes an UploadField, not sure if that's relevant in triggering this, but it's definitely more noticeable at smaller screen sizes.

Issues

• 294

Pull request checklist

• [x] The target branch is correct
  • See picking the right version
• [x] All commits are relevant to the purpose of the PR (e.g. no debug statements, unrelated refactoring, or arbitrary linting)
  • Small amounts of additional linting are usually okay, but if it makes it hard to concentrate on the relevant changes, ask for the unrelated changes to be reverted, and submitted as a separate PR.
• [x] The commit messages follow our commit message guidelines
• [x] The PR follows our contribution guidelines
• [x] Code changes follow our coding conventions
• [x] This change is covered with tests (or tests aren't necessary for this change)
• [x] Any relevant User Help/Developer documentation is updated; for impactful changes, information is added to the changelog for the intended release
• [x] CI is green

[GuySartorelli]

Thanks for raising this!

Since this is a commercially supported module, and commercial support for CMS 4 is now in "security patches only" phase, I can't merge this against the branch it's currently targetting without @colymba saying they're okay with a patch release for the CMS 4 compatible versions.

The alternative would be to retarget this PR to 4.0.

[lekoala]

the edit handler is really broken at the moment see https://github.com/colymba/GridFieldBulkEditingTools/pull/308

for the layout specifically, it also needs fill-height

would be great to have a working feature for the current silverstripe version :)

[GuySartorelli]

Closing in favour of https://github.com/colymba/GridFieldBulkEditingTools/pull/308