As a reminder: latest clingy removed the requirement of having custom context (which made the usage of context.WithValue harder) and uses simple context instead.
Clingy saves the stdin/stdout/stderr to the context (earlier to separated context type) to make it available for unit testing.
Change-Id: I8896574f4670721de43a577cd4b35952e3b5d00e
this allows one to specify a trace id and cause any remote
spans to be sent up to wherever. it doesn't collect any
local traces.
Change-Id: Ia87e294bb276d966f9f3dbfbaf6e7916b1ec7af9
