Apply new GitLab UI for input in admin pages

What does this MR do?

Apply new GitLab UI for input in admin pages

Screenshots (strongly suggested)

Page	Before	After
Edit User
Edit Group
Messages
System Hooks
New Application
New License
New Label
Appearance
General Settings
Repository Settings
CI/CD Settings
Reporting Settings
Metrics and Profiling
Network Settings
Preferences

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• 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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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