fix OpenIfSaved API for DynamoPlayer

[mjkkirschner]

Purpose

update the filePath property of the DynamoView as deserializing the view block of json files relies on it being correct.

@Racel Not sure what you want to do with this change regarding 2.1 x 2.2.
In terms of risk, it's small because this API is not called by many clients, I think only Player calls this, perhaps some extensions as well.

While this does not cause a crash, it does cause graphs to fail to open via player edit button without first closing dynamo.

Declarations

Check these if you believe they are true

• The code base is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning, and are documented in the API Changes document.

Reviewers

@QilongTang

FYIs

@Racel @smangarole

[QilongTang]

@mjkkirschner Can you update the unit tests introduced in #7061?

For example, in the unit test EnsureSaveDialogIsShownOnOpenIfSaveCommand add

ViewModel.OpenIfSavedCommand.Execute(new Dynamo.Models.DynamoModel.OpenFileCommand(openPath));
//assert the path updated 
Assert.AreEqual(ViewModel.FilePath ,openPath);

Other than that, LGTM

[QilongTang]

LGTM