This PR implements JSON RPC-style (i.e. newline delimited) JSON transport. I moved the existing transport tests from DAP to Host and moved the PipeTest base class into TestingSupport so it can be shared by both.
This PR implements JSON RPC-style (i.e. newline delimited) JSON transport. I moved the existing transport tests from DAP to Host and moved the PipeTest base class into TestingSupport so it can be shared by both.