Fix ConfigMap analyzer false positives for operator-managed sidecars

[Copilot]

📑 Description

ConfigMap analyzer flags operator-managed ConfigMaps as unused because sidecars load them dynamically via label selectors rather than Pod spec references. Affects Grafana dashboards, Prometheus rules, and similar patterns.

Changes:

• Added sidecar pattern detection via labels: grafana_dashboard, grafana_datasource, prometheus_rule, fluentd_config
• Added k8sgpt.ai/dynamically-loaded: "true" label for custom patterns
• Added k8sgpt.ai/skip-usage-check: "true" annotation for explicit opt-out
• Matched ConfigMaps skip all analyzer checks (unused, empty, large)

Implementation:

// New helper functions in configmap.go
func isKnownSidecarPattern(cm v1.ConfigMap) bool {
    // Checks for grafana_dashboard, prometheus_rule, etc.
}

func shouldSkipUsageCheck(cm v1.ConfigMap) bool {
    // Checks k8sgpt.ai/skip-usage-check annotation
}

Analyzer now checks these patterns before flagging ConfigMaps, preserving existing detection logic for standard usage.

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

Validated against kube-prometheus-stack: eliminated 29 false positives (28 dashboard + 1 datasource ConfigMaps). Backward compatible - no changes to existing detection behavior.

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