Introduce a RunLogBase type that encapsulates the base information
shared across multiple logs for the same run. This has the information
previously part of the API (Task and RunID), and includes the addition
of a RunScheduledFor timestamp.
Also remove the RunScheduled value for RunStatus, as it was never used
in the scheduler.
This package assists with testing platform.TaskService. The fact that we
use task.PlatformAdapter is just a detail.
This is just a rename, plus one change to support caller-defined
construction of a TaskService (necessary for porting the tests to
enterprise).
Mark Rushakoff
Leonardo Di Donato