Intent of undoRedoService.ts ×18

All 4 exact tests in this concept. Every test is marked by where it enters the hierarchy.

mocha:v1|namespace=vscode@05c208e9e28d8c1c723fa08f85e2b7a96092e8e5|file=vs/ 4 tests
- editor/ 2 tests
  - test/ 2 tests
    
    common/ 2 tests
    
    model/ 1 test
    
    mocha:v1|namespace=vscode@05c208e9e28d8c1c723fa08f85e2b7a96092e8e5|file=vs/editor/test/common/model/modelInjectedText.test|title=Editor Model - Injected Text Events Basic|occurrence=1 Inherited textModel.ts ×6
    
    services/ 1 test
    
    mocha:v1|namespace=vscode@05c208e9e28d8c1c723fa08f85e2b7a96092e8e5|file=vs/editor/test/common/services/modelService.test|title=ModelService maintains undo for same resource and same content|occurrence=1 Inherited undoRedoService.ts ×2
- platform/ 2 tests
  - undoRedo/ 2 tests
    
    test/ 2 tests
    
    common/ 2 tests
    
    mocha:v1|namespace=vscode@05c208e9e28d8c1c723fa08f85e2b7a96092e8e5|file=vs/platform/undoRedo/test/common/undoRedoService.test|title=UndoRedoService multi resource elements|occurrence=1 Inherited undoRedoService.ts ×43
    
    mocha:v1|namespace=vscode@05c208e9e28d8c1c723fa08f85e2b7a96092e8e5|file=vs/platform/undoRedo/test/common/undoRedoService.test|title=UndoRedoService simple single resource elements|occurrence=1 Inherited undoRedoService.ts ×9