Multiple result set support

[GordonBeeming]

Description

Support queries that return multiple result sets (e.g., multiple SELECT statements).

Acceptance Criteria

• Each result set shown as a separate tab in the results pane (Result 1, Result 2, ...)
• Tab shows row count per result set
• Switch between result sets without re-executing the query
• Messages tab aggregates messages from all result sets
• Batch separator (GO) support in the query editor