Allow a user to test timer and timeouts features without waiting for the real world time

[anthonime]

Business workflows may be expressed in terms of hours, days, weeks or months.
Doing integration tests in thoses conditions are impossible.
We must provide a way to allow a library user to configuer Swiffer to transform durations to a unit testable time scale.

Each duration passed to Swiffer should be transformed internally using a DurationTransformer before being passed to SWF.
This include:

• start timer decision timeout
• schedule activity type decision timeouts
• workflow type timeouts
• activity type timeouts
• schedule children workflow decision timeouts
• schedule lambda decision timeouts
• continue as new workflow decision timeouts

Expected interface:

public interface DurationTransformer {
 java.time.Duration transform(Duration requestedDuration);
}

Default implementation is a noop: it just return the request duration.
Another implementation is provided: TestingDurationTransformer with public methods and convenient to use:
public void setDurationOfADay(Duration dayDuration);

The implementation should be provided only during construction of the Swiffer instance.