Fixes backward compatibility to IsaacSim 4.5 for new stage utils

[pascal-roth]

Description

omni.metrics is not part of IsaacSim 4.5, PR restores backward compatibility.

Fixes #4229

Type of change

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

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[pascal-roth]

all tests are passing, only /workspace/isaaclab/source/isaaclab_rl/test/test_skrl_wrapper.py times out

[Mayankm96]

But this still doesn't work for isaac sim version less than 4.5, right?

[pascal-roth]

'omni.metrics' is not available in IsaacSim 4.5, that's why we check before to see if our Isaac version is smaller than 5.0, then we never run the code that wants to import it. We don't maintain compatibility with smaller 4.5 but why should it not work for these versions?