Fixes DCMotor clipping for negative power and adds actuator tests

[jtigue-bdai]

Description

This PR adds tests for actuator initialization, configuration, and computation for Implicit, IdealPD, and DC motor actuators.

This PR also updates the DCMotor model to clip based on a four quadrant DC motor model. This will fix improper clipping in the negative power regions (i.e. positive torque and negative velocity or negative torque and positive velocity).

NOTE: This PR is dependant on the pytest migration in: 2034
This PR includes changes made in 2291 and would be an alternate candidate.

Fixes #2139

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Screenshots

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Checklist

• 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