Improve performance of Sliding Time Window with pane optimization

Currently, the implementation of time-based sliding windows treats each window individually and replicates records to each window. For a window of 10 minute size that slides by 1 second the data is replicated 600 fold (10 minutes / 1 second). We can optimize sliding window by divide windows into panes (aligned with slide), so that we can avoid record duplication and leverage the checkpoint.

I will attach a more detail design doc to the issue.

The following issues are similar to this issue: FLINK-5387, FLINK-6990