Replace all instances of the Pipeline api with the PowerShell api

[TylerLeonhardt]

As mentioned in #641, the Pipeline class is on the chopping block and was not included in PowerShell Standard.

We should replace all Pipeline class usages with the PowerShell class.

I think their APIs are pretty similar so the change is relatively straightforward so I'm making this as Up-for-Grabs

[dee-see]

This was already done in 2.0.0 by #690

[TylerLeonhardt]

Nice catch. Closing