Intent of TestAppendForkSelectTrim_LastBranch

All 2 exact tests in this concept. Every test is marked by where it enters the hierarchy.

go.temporal.io/ 2 tests
- server/ 2 tests
  - common/ 2 tests
    
    persistence/ 2 tests
    
    tests/ 2 tests
    
    TestPGX/ 1 test
    
    TestPostgreSQLHistoryStoreSuite/ 1 test
    
    go.temporal.io/server/common/persistence/tests/TestPGX/TestPostgreSQLHistoryStoreSuite/TestAppendForkSelectTrim_LastBranch Introduced here
    
    TestPGXSP/ 1 test
    
    TestPostgreSQLHistoryStoreSuite/ 1 test
    
    go.temporal.io/server/common/persistence/tests/TestPGXSP/TestPostgreSQLHistoryStoreSuite/TestAppendForkSelectTrim_LastBranch Inherited TestAppendForkSelectTrim_LastBranch