We have some options here:

• migrate the actual RAR implementation to the new TaskEnvironment APIs, handle threading/concurrency issues, etc
• decide that for Multithreaded mode, we will spawn and use the OutOfProc RAR Node
• implement and use a new in-proc RAR Node implementation

Initial thoughts are that we could default to option 2 - using the OutOfProc RAR Node. Need to sync with @ccastanedaucf about how hardened that Node is before comitting to this. This will impact the 'single proc' messaging (because we'd always have another process hosting the RAR node), but that can be solved either by:

• implementing the in-proc RAR node mentioned above, or
• having the MSBuild Server node implement the RAR Client and have the nodes connect to that