Add cudasync

[jychoi-hpc]

This update includes:

• Adding cudasync for timing to synchronize between cpu and gpu
• Add more timers (forward sync and backward sync to measure imbalance)

Ref: https://www.speechmatics.com/company/articles-and-news/timing-operations-in-pytorch

[allaffa]

@jychoi-hpc Black formatting needs to be fixed.