Improve node scanning error messages and adjust severity level if condition is expected

Description

While smoke-testing ACS 4.7.6-rc.1 on OCP 4.19, multiple log entries appear regarding unsupported node scanning.

Example log excerpts:

{"Event":"error analyzing node \"misha-47-central-smhxs-worker-b-trhth\": Node scanning is unsupported for this node","Level":"error","Location":"service.go:49"}
{"Event":"Unable to start node scanning for this namespace","Level":"warning","Location":"detection.go:49","detected namespace":"rhel:9"}
{"Event":"Error scanning node /host inventory: Node scanning is unsupported for this node","Level":"error","Location":"inventorizer.go:58"}

Issues Identified

1. Lack of actionable context

• The message "Node scanning is unsupported for this node" does not explain why scanning is unsupported.
• Users cannot tell if the problem is due to:

• Misconfiguration
• An OCP cluster issue
• An ACS limitation

• No guidance is provided on whether a corrective action exists.

1. Potential misclassification of log severity

• If unsupported node scanning is an expected, recoverable condition, error level is misleading.
• According to logging best practices, error should indicate that the system encountered a problem that prevents normal operation.
• If scanning is simply not available for a given node but the system continues to function, warning or info would be more appropriate.

Expected Outcome

• Add meaningful, user-facing explanation when node scanning is unsupported, including:
  • The reason (e.g., OS version not supported, required agent not present, etc.)
  • Possible user actions (if any)
• Adjust log level from error to warning or info if the condition is expected and recoverable.
• Ensure this applies to all relevant log points in:
• service.go
• inventorizer.go
• detection.go

References

• Related PR modifying logs: stackrox/stackrox#5469
• Commit introducing current message: 51d64f3
• https://redhat-internal.slack.com/archives/C08CM7QDETH/p1754904045357419