docs: update nodescan rfc

[alegrey91]

Description

Fix #1206

Test

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Additional Information

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Potential improvement

Checklist

• I have read and understood the Kubewarden AI Policy

[Copilot]

Pull request overview

Updates the Node Scan RFC to reflect the latest NodeScanConfiguration/NodeScanJob workflow and lifecycle semantics requested in #1206, clarifying how periodic vs. immediate scans are triggered and how resources are garbage-collected.

Changes:

• Makes scanInterval explicitly mandatory and frames NodeScanConfiguration as the periodic scan scheduler.
• Documents an immediate-scan trigger via force-node-scan: "true" annotation with automatic removal after completion.
• Updates the RFC to reflect inverted ownership/GC semantics: NodeScanConfiguration owns jobs/SBOMs (Kubernetes GC), while node deletion requires controller-driven cleanup.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.78%. Comparing base (5adb1bd) to head (b61805c).
⚠️ Report is 113 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1207      +/-   ##
==========================================
- Coverage   53.44%   52.78%   -0.67%     
==========================================
  Files          61       77      +16     
  Lines        5340     6472    +1132     
==========================================
+ Hits         2854     3416     +562     
- Misses       2088     2582     +494     
- Partials      398      474      +76     

Flag	Coverage Δ
unit-tests	52.78% <ø> (-0.67%)	⬇️

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[flavio]

@alegrey91 WARNING: you will probably have to close this PR and open it against the kubewarden/docs this is a change to the RFC, hence it's fine to do it here

[fabriziosestito]

Please address the missing comment

[fabriziosestito]

@alegrey91, I'm merging this. The comment in #1207 (comment) is still unresolved, but I'll address it during a second pass on the RFC.