Provider helpers to easily overwrite Url query parameters

[heaths]

According to the REST API guidelines, clients should set or overwrite the api-version header for any request to the service including pageables and LROs; however, url::Url doesn't define an easy way of overwriting headers. We have helpers for appending and should add some for setting/overwriting because the code to do so - which we need to do for every request to the service - is a bit verbose.

See this comment for context.