Intent of TestMergeReports_MultipleReports

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
  - tools/ 3 tests
    
    testrunner/ 3 tests
    
    go.temporal.io/server/tools/testrunner/TestMergeReports_MissingRerun Inherited TestMergeReports_MissingRerun
    
    go.temporal.io/server/tools/testrunner/TestMergeReports_MultipleReports Introduced here
    
    go.temporal.io/server/tools/testrunner/TestWriteCurrentReport Inherited testrunner.go ×6