Refactor tests to get some code sharing with distributed-process

[hyperthunk]

This will involve collaboration with the CH maintainers, but is worthwhile IMO. Updating title to reflect change of focus.

[rodlogic]

After spending a bit of time looking at distributed-process tests, I am wondering if we can abstract some of the test case boiler plate for testing local/remove and assertions within/without platform server processes.

[hyperthunk]

@rodlogic I think that's a good idea.

[hyperthunk]

also see issue #14 and https://github.com/hyperthunk/distributed-process-platform/blob/timer/tests/TestTimer.hs