feat(alerts): Add memory utilization rules

[nfebe]

Add container memory utilization to alert rules and dashboards while keeping raw memory usage available in bytes.

[sourceant]

Code Review Summary

This PR adds container memory utilization metrics to alert rules and dashboards. The changes include UI updates for clarity, such as metric-specific hints and explicit unit labels, along with corresponding unit handling in dashboard panels and a regression test.

🚀 Key Improvements

• Introduced container.memory.utilization metric support.
• Added a hint property to metric options in AlertRulesPanel.vue for better user guidance.
• Updated labels to clearly distinguish between raw memory usage and percentage-based utilization.
• Ensured correct unit rendering in dashboard PanelCard components.

💡 Minor Suggestions

• In the future, consider using the METRIC constant in PanelCard.vue and PanelEditorModal.vue instead of hardcoded strings to ensure consistency with AlertRulesPanel.vue.

[sourceant]

Review complete. No specific code suggestions were generated. See the overview comment for a summary.