This PR adds support for generating randomized workloads that will be executed
against a simulated cluster, as well as against a correctness model. Initially
this just generates ScanAll and CreateVertex requests, and anything that it
creates, it also inserts into a `std::set`, and when we do a ScanAll, it asserts
that we get the same number of requests back. This will become much more
sophisticated over time, but it's already hitting pay-dirt.
* Create LocalTransport Io provider for sending messages to components on the same machine
* Move src/io/simulation/message_conversion.hpp to src/io/message_conversion.hpp for use in other Io providers
