Same as RELAX_VISIT_TIMES_AND_SEQUENCE_AFTER_THRESHOLD, but the
vehicle is also relaxed: visits are completely free at or after the
threshold time and can potentially become unperformed.
Visit start times and vehicle start/end times will be relaxed, but
each visit remains bound to the same vehicle and the visit sequence
must be observed: no visit can be inserted between them or before
Same as RELAX_VISIT_TIMES_AFTER_THRESHOLD, but the visit sequence
is also relaxed: visits remain simply bound to their vehicle.
Implicit default relaxation level: no constraints are relaxed,
i.e., all visits are fully constrained.