Improve UX project/group ci variables

What does this MR do?

Improves the new project/group CI variables UX, currently behind feature flag new_variables_ui

• Sorts variables by keys in ascending order
• Sets table to fixed width
• Popover for key, value and environment_scope with copy value button
• Fixes issues with UX regarding masking a variable
• Represent masked and protected boolean values with icons
• Modal layout changes
• Sends back variable_type to groups

UX Walkthrough Video

https://youtu.be/GT2ViXuAQ1Q

Screenshots

Table

Add variable

Update variable

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