(v3.5.1) - WandBLogger compability with previous WandB sessions

[AlejandroCN7]

Description

This PR makes the WandBLogger wrapper compatible with pre-existing WandB sessions. Additionally, some related details have been improved in the tool. For more information, see the changelog.

Motivation and Context

We've noticed that Sinergym can be used in scripts where a WandB session has already been started. The wrapper was incompatible with this use case, such as when using sweeps.

Now, the wrapper can be used with a pre-existing WandB session, without the need to specify the entity or project (which, if provided, will be ignored). It still allows specifying other parameters during construction, maintaining full functionality of the wrapper.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• 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)
• Improvement (of an existing feature)
• Others

Checklist:

• I've read the CONTRIBUTION guide (required)
• My change requires a change to the documentation.
• I have updated the tests.
• I have updated the documentation accordingly.
• I have reformatted the code using autopep8 second level aggressive.
• I have reformatted the code using isort.
• I have ensured cd docs && make spelling && make html pass (required if documentation has been updated.)
• I have ensured pytest tests/ -vv pass. (required).
• I have ensured pytype -d import-error sinergym/ pass. (required)

Changelog:

• WandbLogger: Added compatibility with wandb created sessions previously.
• WandBLogger: Episode summary will not be dump with an empty episode.
• Scripts (train_agent.py): Fixed default experiment name in order to be compatible with artifact save supported names.
• Callbacks (LoggerEvalCallback): Fixed case when several evaluation episodes are set up.
• Documentation: WandBLogger section updated with this new feature.