Update WorkerOptions to have a URI property instead of host name and port number

[Francisco-Gamino]

This is related to #992.

We are updating the logic to parse command-line arguments that the PowerShell language worker receives from the Functions Host. Currently, we are adding support to parse the new arguments, which are prefixed with functions-.

After the Functions Host changes have propagated, and we have a Core Tools version with this new Functions Host, we should remove parsing support for the old arguments. When doing this work, we should also consider adding a Uri property to the WorkerOptions type and assigning workerArgs.FunctionsUri to it. With this update, we can avoid rebuilding the uri string inside the MessagingStream method and pass the WorkerOptions instance to that method instead.