Allow users to edit Model Registry resource names and add support for sorting by resource name

[dhirajsb]

Is your feature request related to a problem? Please describe.
Model Registry used to depend on mlmd as it's backing metadata store, which had a uniqueness constraint on resource names. And it also didn't support editing resource names.

Model Registry added support for duplicated names in a parent resource scope by using an id prefix for resource names. It was a workaround to accomodate MLMD.

This requirements should be dropped and names should be made editable and unique within a parent scope without having to use a parent prefix id. This will also allow the API to support sorting output by Name property.

Describe the solution you'd like
Now that Model Registry has direct access to the underlying DB and has full control over the schema, it can do the following:

• Add an ownerContextId column
• Replace the unique name constraint with a unique name+ownerContextId constraint

That way names only need to be unique within a parent scope. Global or parent less resources can use a NULL ownerContextId, making such resource names globally unique.

Describe alternatives you've considered
N/A

Additional context
This affects other features being added to Model Registry such as #1224 .