proposed fix for RunningMeanStd overflow

[spiglerg]

Connected to Issue https://github.com/DLR-RM/stable-baselines3/issues/1953

Description

RunningMeanStd is made robust to overflows with two modifications:

• the product that can produce overflows when `count' becomes too large is split into a product of smaller quantities;
• overflow exceptions are detected, and in that case normalization counts are rescaled, and the function is called again.

Motivation and Context

• Issue https://github.com/DLR-RM/stable-baselines3/issues/1953

• Closes #1953

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

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)

Checklist

• [x] I've read the CONTRIBUTION guide (required)
• [ ] I have updated the tests accordingly (required for a bug fix or a new feature).
• [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)
• [x] I have checked that the documentation builds using make doc (required)