Add support for filtering resource properties and returning unique values

[dhirajsb]

Is your feature request related to a problem? Please describe.
Currently, when model registry returns resource values (either for one resource or in a list) it returns all the values and customProperties for the resource.
The client may not need all the properties in every query and list operation. This will help minimize the amount of data returned and speed up operations.
Also, adding support for a way to return distinct values will help satisfy use cases like getting a list of all unique metric or parameter names.

Describe the solution you'd like

• Add a parameter called properties for specifying a list of resource property names to select from model registry.

• A special name customProperties in the list will allow selecting (or not selecting if missing) resource customProperties.

• Another boolean property called distinct (false by default) will allow selecting distinct value when set to `true.

Describe alternatives you've considered
None

Additional context
This is related to new functionality needed for the Kubeflow Pipelines KEP mprahl/kubeflow-community#1 for Experiment tracking integration.

[dhirajsb]

@jonburdo CC