(v3.3.2) - Calibration of observation normalization improvement

[AlejandroCN7]

Description

This PR brings some improvements related with NormalizeObservation wrapper calibration, more information in referenced issue

Motivation and Context

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

Fixes #409

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)
• [x] Improvement (of an existing feature)
• [ ] Others

Checklist:

• [x] I've read the CONTRIBUTION guide (required)
• [x] My change requires a change to the documentation.
• [] I have updated the tests.
• [x] 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:

• Wrapper flexibility for use list or numpy in mean and var calibration.
• Functionality to save this values in Sinergym output folder as txt files.
• Deleted related process in example scripts.
• Updated wrapper documentation and notebook example explaining the use case.