Add security attributes column to inventory

What does this MR do and why?

Add security attributes column to inventory

If security_context_labels feature flag is enabled,
show security attributes column in security inventory

In project attributes cells, show gl-labels for the first 3 attributes
and an overflow attribute with a popover that shows the full list
Reuse client resolvers that return mock attributes for the project page

References

• epic: Security Attributes/Context Filtering (&18010)
• issues:
  • Frontend: Scaffold `Security attributes` column... (#550478 - closed)
  • Frontend: Show project attributes in inventory ... (#550491 - closed)
• design: #547963[Security_inventory-_group-level_-_security_labels_-_overflow_labels.png]

Screenshots or screen recordings

Before/Feature flag disabled	After/Flag enabled

How to set up and validate locally

git checkout 550478-make-attributes-space-in-security-inventory
echo "Feature.enable(:security_context_labels)" | gdk rails c

1. go to a group that has at least one project => sidebar => Secure => Security inventory
2. there should be a new Security attributes column in the table
   • the first three attributes are shown in the table cell
   • hovering over +N more should show all attributes in a popover
   • eventually clicking the cell will open a drawer (not implemented yet)
3. each project should have the same four mocked attributes for now (until we have a way to query for attributes via GraphQL)

MR acceptance checklist

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Related to #550478 (closed)