NewSuspendableClock creates a new SuspendableClock.

SuspendableClock is a decorator for Clock that allows Timers and Contexts with timeouts to be suspended temporarily.

UnsuspendedDurationKey instances can be provided to Context.Value() to obtain the total amount of time a SuspendableClock associated with the Context object was not suspended, since the creation of the Context.

Suspendable is an interface type of the methods of SuspendableClock that are used by NewSuspendingBlobAccess() and NewSuspendingDirectoryFetcher().