Avoid torch type-error under torch.compile

[amjames]

Description

In RolloutBuffer.compute_returns_and_advantage a numpy array with dtype bool is used as a, operand for subtraction with a python scalar. This relies on some automatic casting rules which pytorch does not support (in particular promoting bool arrays to int/float). When this region is hit by torch-compile a runtime error is encountered. Casting the bool array to an integer dtype resolves the issue.

After the changes at https://github.com/pytorch/pytorch/pull/124481 land, the example presented in this issue will successfully compile with this small change.

Motivation and Context

This change has no observable impact on the behaviors of programs executed normally. It prevents an error when a user's program uses torch-compile.

If this change is not desired the closed PR will document a work-around for anyone who hits this issue.

Types of changes

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

Probably the closest option, but I wouldn't classify this as a bug. The issue is only present when a program is manipulated by a 3rd party library.

• [ ] 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)
• [ ] 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.
• [ ] I have opened an associated PR on the SB3-Contrib repository (if necessary)
• [ ] I have opened an associated PR on the RL-Zoo3 repository (if necessary)
• [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)

Note: You can run most of the checks using make commit-checks.

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