Intent of TestPollScalingUpOnBacklog

All 3 exact tests in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 3 tests
- server/ 3 tests
  - service/ 3 tests
    
    matching/ 3 tests
    
    TestPhysicalTaskQueueManager_Fair_TestSuite/ 3 tests
    
    go.temporal.io/server/service/matching/TestPhysicalTaskQueueManager_Fair_TestSuite/TestPollScalingDecisionsAreRateLimited Inherited TestPollScalingDecisionsAreRateLimited
    
    go.temporal.io/server/service/matching/TestPhysicalTaskQueueManager_Fair_TestSuite/TestPollScalingNonRootPartition Inherited TestPollScalingNonRootPartition
    
    go.temporal.io/server/service/matching/TestPhysicalTaskQueueManager_Fair_TestSuite/TestPollScalingUpOnBacklog Introduced here