Fixed the `PipeWriterStream` to properly detect a canceled write and throw an `OperationCanceledException` in those cases. And making sure `Complete` is called in a safe manner by ensuring it is in a lock so writes can't be in-progress.
Part of #4246
Changes:
* Update source code layout to follow the new conventions for this repo
* Update project files to use `<Reference>`
* Update targets to build NPM packages
* Update BuildTools to support custom 'restore' and 'test' targets
Brennan Conroy
Nate McMaster