Adds null-space control option within OperationSpaceController

[ozhanozen]

Description

This PR adds an option to enable null-space control within OperationSpaceController (following the discussions in #913).

Details

Currently, OperationSpaceController controls only the task space, which results in joint movements within the null-space of redundant robotic manipulators. In general, it is desirable to have some control over the robot null-space, e.g., to prevent the joints from going near their limits. Hence, the PR adds the following:

• An optional nullspace (position) control integrated into OperationSpaceController. This controller attracts the robot joints to provided targets whereas possible, in parallel to the task-space target.
• Test cases for OperationSpaceController that use null-space control.
• Updates to the related tutorial script and documentation to use and describe null-space control.
• Integration of (optional) null-space control to OperationSpaceControllerAction with predefined joint targets, e.g., default joint positions, joint centers, zero joint position.
• Integration of null-space control to "Isaac-Reach-Franka-OSC-v0" manager-based environment.

Null-space control utilizes either the dynamically consistent Jacobian inverse or the Moore–Penrose inverse, depending on whether the full inertia matrix is available.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

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