Support det+cls+rec online prediction pipeline, improve RecResizeNormForInfer to fix bug in single img predict_rec

[HaoyangLee]

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Motivation

• Add predict_cls and det+cls(optional)+rec online prediction pipeline.
• When run single image prediction in predict_rec.py, padding=False, keep_ratio=True, target_width=None, which will raise bug in RecResizeNormForInfer. Now fix it to support target_width=None.

Related Issues and PRs

Issue #238