BREAKING CHANGE:
Before:
```
testComponentBuilder.createAsync(MyComponent).then(root: RootTestComponent => {
}
```
After:
```
testComponentBuilder.createAsync(MyComponent).then(fixture: ComponentFixture => {
}
```
Closes #4711
BREAKING CHANGE:
Before:
```
testComponentBuilder.createAsync(MyComponent).then(root: RootTestComponent => {
}
```
After:
```
testComponentBuilder.createAsync(MyComponent).then(fixture: ComponentFixture => {
}
```
Closes #4711