Resolve "Prevent accidental deletions via soft delete for groups" - UI changes (MR: 5/n)

What does this MR do?

For #33257 (closed)

MR 5/n

I am splitting this feature into multiple MRs.

This is the 5th MR which adds necessary changes to help perform

1. Mark a group for soft-deletion via UI
2. Restore an already soft-deleted group to original state via UI.
3. Show "pending-delete" labels for groups that are marked for deletion.
4. In group show page and the show pages of it's subgroups and projects, show notices about pending delete.

Screenshots

Remove group setting:

Remove group confirmation:

Redirected to group page with notice after confirming deletion:

Restore group setting:

'pending delete' label on group tree page:

Group show page of a group that is scheduled for deletion (shows "This group, it's subgroups and projects has been scheduled for removal on (a date) label.):

Subgroup show page - when it's parent group has been marked for deletion (shows label about parent group's pending deletion):

Project show page - when it's parent group has been marked for deletion (shows label about parent group's pending deletion):

admin/groups page - shows badge for groups pending deletion:

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team