[BugFix] Fix a bug in the augmentation of FFSP instances

[LTluttmann]

Description

Fixes a bug in the augmentation of a FFSP instance, where stages were assigned the wrong machines in the pre_step of the environment.

Also added marginally faster tensordict dataset which uses slightly (around 30%) more CPU and improved the MatNet code a little bit.

Motivation and Context

Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.
You can use the syntax close #15213 if this solves the issue #15213

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Types of changes

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

Checklist

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• 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.