Add `--eval-env-kwargs` to `train.py`

[Quentin18]

Description

Motivation and Context

• [x] I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation (update in the documentation)

Checklist:

• [x] I've read the CONTRIBUTION guide (required)
• [x] I have updated the changelog accordingly (required).
• [ ] My change requires a change to the documentation.
• [ ] I have updated the tests accordingly (required for a bug fix or a new feature).
• [ ] I have updated the documentation accordingly.
• [x] I have reformatted the code using make format (required)
• [x] I have checked the codestyle using make check-codestyle and make lint (required)
• [x] I have ensured make pytest and make type both pass. (required)

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[araffin]

Hello, I somehow cannot push to your branch, so I pushed my edits to https://github.com/DLR-RM/rl-baselines3-zoo/pull/406 I mostly fixed a breaking change (by default, eval-env-kwargs should be the same as env-kwargs which was not the case here anymore) and simplify tests (and added a runtest for that feature).

[Quentin18]

OK thanks :+1: