ROX-30873: Remove export buttons from legacy dashboard

[sachaudh]

Description

Removed export functionality from the legacy vulnerability management dashboard.

Key Changes:

• Deleted FixableCveExportButton component entirely
• Removed export buttons from vulnerability management list and entity page layouts
• Stripped CSV export functions (exportCvesAsCsv, getCvesInCsvFormat) from VulnerabilitiesService
• Removed export-related state management and loading indicators from dashboard components
• Cleaned up unused imports and utility functions (getCveExportName) in vulnerability utils
• Eliminated export handlers for Image, Node, and Cluster CVE types
• Removed backdrop loading overlay for export operations

User-facing documentation

• CHANGELOG.md is updated OR update is not needed
• documentation PR is created and is linked above OR is not needed

Testing and quality

• the change is production ready: the change is GA, or otherwise the functionality is gated by a feature flag
• CI results are inspected

Automated testing

• added unit tests
• added e2e tests
• added regression tests
• added compatibility tests
• modified existing tests

How I validated my change

Before

After

[openshift-ci]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[rhacs-bot]

Images are ready for the commit at d601f96.

To use with deploy scripts, first export MAIN_IMAGE_TAG=4.9.x-751-gebb31d4984.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.85%. Comparing base (1959e3a) to head (d601f96).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #16801      +/-   ##
==========================================
- Coverage   48.85%   48.85%   -0.01%     
==========================================
  Files        2686     2686              
  Lines      200796   200796              
==========================================
- Hits        98099    98097       -2     
- Misses      95079    95081       +2     
  Partials     7618     7618              

Flag	Coverage Δ
go-unit-tests	48.85% <ø> (-0.01%)	⬇️

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