Add momentum to the LearningRateMonitor
🚀 Feature
We should add a flag to optionally log the momentum value (for optimizers that have the attribute) in our LearningRateMonitor.
Motivation
Some learning rate schedulers (eg. OneCycle) also adjust the momentum value when updating the learning rate.
Pitch
For each scheduler's optimizer, we can check to see if it has a momentum attribute. If so, we log the value in addition to the learning rate.