Summary

Implements a priority queue system for provisioner jobs to ensure human-initiated workspace builds are processed before prebuild jobs, improving user experience during high queue periods.

Changes

• Queue Logic: Updated AcquireProvisionerJob query to use CASE WHEN on initiator_id to order by priority
• Priority Assignment: Human-initiated jobs get priority 1, prebuilds get priority 0 (via SQL CASE WHEN)
• Testing: Updated comprehensive test to verify priority queue behavior using initiator_id

How it works

1. The AcquireProvisionerJob query now uses a CASE WHEN statement to prioritize jobs:
   • Jobs with initiator_id != PrebuildsSystemUserID get priority 1 (human-initiated)
   • Jobs with initiator_id = PrebuildsSystemUserID get priority 0 (prebuilds)
2. The query orders by this calculated priority first, then creation time
3. This ensures human jobs are always acquired before prebuild jobs, regardless of creation time

Testing

• Updated unit test that verifies priority-based job acquisition
• Test creates both human and prebuild jobs and confirms acquisition order
• Existing tests continue to pass as the change is backward compatible

Impact

• Users: Faster workspace build times when prebuilds are queued
• System: No performance impact, just changes query ordering
• Backward Compatibility: No migrations required, works with existing data

Related to provisioner queue issues like #15843 and #16488 - this addresses the specific case where prebuilds can delay human-initiated workspace builds during busy periods.