Add setter for epoch in iteration

[b-chu]

What does this PR do?

This allows the user to set the epoch in the iteration. This is needed for PPO to signal to early break out of an iteration by setting the epoch to the max number of epochs in an iteration.

What issue(s) does this change relate to?

Before submitting

• Have you read the contributor guidelines?
• Is this change a documentation change or typo fix? If so, skip the rest of this checklist.
• Was this change discussed/approved in a GitHub issue first? It is much more likely to be merged if so.
• Did you update any related docs and document your change?
• Did you update any related tests and add any new tests related to your change? (see testing)
• Did you run the tests locally to make sure they pass?
• Did you run pre-commit on your change? (see the pre-commit section of prerequisites)

[mvpatel2000]

Please add unit test