Generate guid for FormatViewDefinition InstanceId if not provided

[SteveL-MSFT]

PR Summary

InstanceId for a FormatViewDefinition is the key to help differentiate views with the same name for the same type. However, when using the constructor for FormatViewDefinition that doesn't take an InstanceId, it keeps the default guid value of all zeros. During export time, the cmdlet builds a dictionary with the InstanceId as the key and with multiple views with same key, you only get the first one. Fix is to generate a new guid for InstanceId if one is not provided.

PR Context

Fix #11825

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[ghost]

🎉v7.1.0-preview.1 has been released which incorporates this pull request.:tada:

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