Fix MAGN-5376 Element.Geometry not working after reopening file.

<h4>Summary</h4>

I am regenerating the document before attempting to get geometries from elements. This will fix the defect. But because the test cases are running without starting a transaction, I am modifying the test framework to start a transaction in the setup method.

I added a new method OnEvaluationStarted which will be called at the beginning of an evaluation process. This method is overridden in RevitDynamoModel so that a new transaction can be started.

I am removing one call to ForceCloseTransaction in DocumentManager.Regenerate because it will be duplicated with the one call in RevitDynamoModel.OnEvaluationCompleted.

<h4>Reviewers</h4>
- [ ] @lukechurch 
- [ ] @pboyer 
When some operations are done when the application is in an idling state, the transaction need to be committed. Originally the regeneration is done in a separate task, so this is needed. But now it is done together with other operations, so this is not required because at the end of the evaluation process, the transaction will be committed.