Fixes default joint pos when setting joint limits

[kellyguo11]

Description

When setting joint limits, the existing default joint positions can fall outside of the bounds of the new joint limits. This change clips the default joint positions to ensure they are within the bounds of the new limits.

Type of change

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

Checklist

• [x] I have run the pre-commit checks with ./isaaclab.sh --format
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] 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