Enable serialize/deserialize navigation property with count without content

[xuzhg]

Short summary (3-5 sentences) describing the issue.

Reproduce steps

ODL enables $count after navigation property in the $expand, for example

~/$expand=$navProp/$count
~/$expand=$navProp/$count($filter=prop gt abc)
~/$expand=$navProp/$count($search=prop)

See details at: #2051

When doing serialization, the navigation property should only contain the odata.count annotation without content.

Expected result

The payload should be:

{

    "[email protected]": 4
}

Actual result

{

    "[email protected]": 4,
    "navProp": []
}

Additional detail

• We'd also need to support to read the navigation property without content but contains the odata.count.