ROX-31479: Add getting nodes for CVE

[mtodor]

Description

This PR adds the ability to fetch information if there are nodes affected by a specific CVE.

It groups nodes by cluster and OS image used. This is done because mostly cluster nodes are using the same image and usually contain the same set of CVEs.

We are using the streaming (export) endpoint in this case, because filtering by CVE is not possible in the list nodes endpoint, and filtering is really important.

Validation

• Unit tests
• Tested with MCP inspector against demo staging cluster
• Tested with LLM against demo staging cluster

LLM testing: (redacted)

> Is this CVE affecting me CVE-2020-26159?

⏺ stackrox-mcp - get_deployments_for_cve (MCP)(cveName: "CVE-2020-26159")
⏺ stackrox-mcp - get_nodes_for_cve (MCP)(cveName: "CVE-2020-26159")

⏺ Yes, CVE-2020-26159 is affecting your environment, but only at the node level - not in your application deployments:

  Affected Nodes:
  - staging-<abc>-cluster: 8 nodes
    - OS: Red Hat Enterprise Linux CoreOS V123-0 (Plow)
  - staging-<def>-cluster: 6 nodes
    - OS: Red Hat Enterprise Linux CoreOS V124-0 (Plow)

  Total: 14 nodes affected across 2 clusters

  Deployments: None of your application deployments are affected by this CVE.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 89.15663% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.38%. Comparing base (bf6db65) to head (434f67d).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/toolsets/vulnerability/nodes.go	89.02%	5 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
+ Coverage   85.00%   85.38%   +0.38%     
==========================================
  Files          23       24       +1     
  Lines         820      903      +83     
==========================================
+ Hits          697      771      +74     
- Misses         96      101       +5     
- Partials       27       31       +4     

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