leverage IODataClientFactory to Use HttpClient in OData Client

[chuanboz]

in Use HttpClient in OData Client, it talked about how to use HttpClient in OData Client, and includes lots of sample code to make that work. With the addtion to ODataClient extensions (https://github.com/OData/Extensions/), there is new way to use HttpClient in ODataClient, very similar to IHttpClientFactory experience and would work out of box.

The issues is to add public document for that out of box usage and link this to that page.
@xuzhg FYI.