WIP: [FE] Add "Filter results" control on Group Value Stream Analytics

What does this MR do?

This MR addresses the FE changes for #217943 (closed)

Feature Flag

Required feature flag: value_stream_analytics_filter_bar

TODO

• Feature flag for filter bar
• Add skeleton ui for filter bar
  • Clean up responsive styling
  • Replace utility classes with gl- equivalents
• Add Tokens
  • Label
  • Milestone
  • Author
  • Assignees
• Update filter values in the vuex store
  • Populate filter bar with query parameters from the BE on load
  • Persist filter selections in query parameters
• Disable task by type filters when label filters are active needs investigation
• Update API requests for filtering to include additional params
• Update filter bar styling
• Refetch token data when typing

Screenshots

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

Closes #217943 (closed)