mrae.fit() training loop needs early stopping mechanism

[m-nolan]

mrae/mrae/MRAE.py

Line 111 in a32fd63

for epoch_idx in tqdm(range(max_epochs)):

The current training loop runs and optimizes the model to minimize training loss. This has no stop point beyond the max iterations argument.

This needs an early stopping mechanism, either a moving average of the loss delta, some train/valid loss crossover, etc.

Test with the sample dataset.
Add a test with random data (?) to show that it works to stop training if it isn't learning anything.