operators: ignore node deletion errors on absence

[burgerdev]

Context

If a node deletion operation fails transiently after the instance was deleted at the CSP, we need to ensure that the retry succeeds, even if the instance we attempt to delete is already gone at the CSP.

Example operator logs: https://gist.github.com/burgerdev/c80de86ae44552a383364ef031243a41

Proposed change(s)

• AWS: Ignore the specific error message for missing images.
• Azure: nothing - deleting absent instance IDs is no error here.
• GCP: turn on SkipInstancesOnValidationError, which is designed for this use case.

Additional info

• AB#3533

Checklist

• [x] Run the E2E tests that are relevant to this PR's changes
  • [x] upgrade test on GCP
  • [x] upgrade test on AWS post-merge
• [x] Add labels (e.g., for changelog category)
• [x] Is PR title adequate for changelog?
• [x] Link to Milestone

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Coverage report

Package	Old	New	Trend
operators/constellation-node-operator/internal/cloud/aws/client	34.40%	34.60%	:arrow_upper_right:
operators/constellation-node-operator/internal/cloud/gcp/client	43.80%	43.90%	:arrow_upper_right: