Make 'HttpResponseContext' not needed in PS function script

[daxian-dbw]

Make HttpResponseContext not needed in PS function script.

To properly convert a value for a specific output binding name implicitly, we need to know the metadata of the binding referred by that name, such as the type of the output binding.
The changes in this PR register the output binding metadata to a concurrent dictionary with the Runspace's InstanceId as the key before start running a function script, and then un-register after the function script finishes running. When a function script that calls Push-OutputBinding is running, we can figure out the current Runspace by Runspace.DefaultRunspace, and then we can query for the output binding metadata by using the InstanceId.

This approach take into the concurrency support that we will have in future. Push-OutputBinding is able to get the metadata about the function script that is running even with multiple Runspaces/PowerShellManagers processing requests at the same time.

Fix #93

[TylerLeonhardt]

LGTM - a couple nits.

I was wondering if we could hold off on coupling the FunctionLoader and the PowerShellManager just to keep the separation of concerns but I can't think of a way to keep it that way.

[TylerLeonhardt]

Looks like there's a CI failure. I think you missed including the Resources file?

[daxian-dbw]

It turns out the .gitignore cause the resource.psd1 file to be ignored.

[daxian-dbw]

I was wondering if we could hold off on coupling the FunctionLoader and the PowerShellManager just to keep the separation of concerns but I can't think of a way to keep it that way.

@TylerLeonhardt and I chatted about this offline. This PR doesn't introduce coupling between FunctionLoader and PowerShellManager. FunctionMetadata serves as a store that holds the function metadata information for the function script that is running in each Runspace (query key is the Runspace's InstanceId). The function metadata is registered before a PowerShellManager runs the corresponding function script, and is unregistered after the corresponding function script is done running.