Ignore blank fields in analytics view, more comments, and widget edit

[jkru3]

Update analytics view SQL and dashboard widgets

Description:
This CL updates the SQL logic for the GKE Maintenance Analytics view and makes improvements to the GKE Maintenance Dashboard widgets.

Analytics View SQL (README.md) Updates:

• Improved Robustness for Missing Values: Chained NULLIF(..., '') across JSON payload extractions to safely handle empty annotation strings and catch Go's zero-time formatting ('0001-01-01T00:00:00Z').
• Enhanced State Ranking: Introduced a status_rank column and refined CASE statements to precisely determine the cycle's final aggregated state (e.g. prioritizing COMPLETE, DELETED, ONGOING, PENDING, and ignoring UNKNOWN cases).
• Comment Organization: Expanded the analytical SQL's inline comments, breaking the logic out into clear, labeled stages (e.g., 1. EXTRACT RAW LOGS, 2. PRE-PARSE LOGS) to outline the state machine visually.

Dashboard Widgets & Layout (gke-maintenance-dashboard.json) Updates:

• P95 Threshold Refinements: Changed the "Avg days" and "P95 hours maintenance downtime" widget to properly calculate thresholds in hours (dividing by 3600).

[jkru3]

Great catches Floyed, Thank you :)