Add TimeStopping callback

[zaleslaw]

It's an exciting idea to limit the training via the maximum limit of training time.

The idea is implemented in tf-addons and could be adopted in KotlinDL

The desired PR addressing this issue should include:

• Implementation of TimeStopping callback
• Documentation
• Integration test with callback (see LeNetWithEarlyStoppingCallback )

P.S. If you want to take this ticket, please leave the comment below
P.P.S Read the Contributing Guidelines.

The reference implementation could be taken from tensorflow-addons

[mkaze]

I'll take this one.

[zaleslaw]

Great @mkaze, assigned on you, if you have any ideas about callbacks feel free to share it here on make a topic in discussions