UI for disabling group/project email notifications

What does this MR do?

Front end changes needed for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30755 and https://gitlab.com/gitlab-org/gitlab-ce/issues/50020

If the group or project owner has disabled email notifications, then we want to reflect that status in the areas where the user can change their notifications.

Where	Before	After
Issue/MR sidebar
User Profile Notification settings
Group/Project header
Group owner settings (Permissions, LFS, 2FA)
Project owner settgins (Visibility, project features, permissions)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created : Tech review issue https://gitlab.com/gitlab-org/gitlab-ce/issues/66164
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

Closes #50020 (moved)