[SPARK-29345] Add an API that allows a user to define and observe arbitrary metrics on batch and streaming queries

• Type: Epic
• Status: Resolved
• Priority: Major
• Resolution: Done
• Affects Version/s: 3.0.0
• Fix Version/s: 3.0.0
• Component/s: SQL
• Epic Name: Observable Metrics for Streaming queries
• Target Version/s: 3.0.0
• Assignee: Herman van Hövell
• Reporter: Herman van Hövell
• Created: 03/Oct/19 10:56
• Updated: 17/Jun/20 06:33
• Resolved: 17/Jun/20 06:33