Make DeadlineMovingAverageModel to work with context

[Mr-Geekman]

🚀 Feature Request

We want to teach DeadlineMovingAverageModel to work with context to enable inference mode.

Proposal

1. Make DeadlineMovingAverageModel the child of NonPredictionIntervalContextRequiredAbstractModel instead of NonPredictionIntervalContextIgnorantAbstractModel.
2. Change NonPredictionIntervalContextIgnorantModelMixin into NonPredictionIntervalContextRequiredModelMixin.
3. Fix _DeadlineMovingAverageModel to work with context.
4. Fix PerSegmentModelMixin to work with prediction size, there probably will be some problems.
5. Fix tests on test_inference to work with a new type of model.

Test cases

1. Make sure current tests pass.
2. Modify tests for DeadlineMovingAverageModel.
3. Fix test_inference tests.

Additional context

No response

[Mr-Geekman]

Solved via #917.