ROX-31479: Add get clusters for CVE

[mtodor]

Description

This PR is adding fetching of clusters affected by a CVE.

Validation

• Unit tests
• Tested with LLM

Testing example

Prompt: Is this CVE affecting me RHSA-2024:6412?
LLM called all 3 tools and responded:

  - Clusters affected: 1 cluster
    - staging-secured-cluster
  - Deployments affected: None
  - Nodes affected: 6 nodes

Prompt: Is affected by CVE-2021-12345?
LLM: didn't call get clusters by CVE tool

Prompt: (cluster does not exist) Is dev-infra-cluster affected by CVE-2021-12345?
LLM called all 3 tools without cluster filter and responded:

CVE-2021-12345 is not affecting any clusters, deployments, or nodes in your entire infrastructure, including dev-infra-cluster.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.18750% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.78%. Comparing base (8c77a67) to head (a2fdc52).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/toolsets/vulnerability/clusters.go	91.66%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #20      +/-   ##
==========================================
+ Coverage   85.38%   85.78%   +0.40%     
==========================================
  Files          24       25       +1     
  Lines         903      964      +61     
==========================================
+ Hits          771      827      +56     
- Misses        101      104       +3     
- Partials       31       33       +2     

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