apply_joint_force: Simplified using ComponentDefault

[peci1]

🦟 Bug fix

Summary

ComponentDefault has been added quite some time ago. I've noticed the JointForceCmd component tutorial still uses the cumbersome if (component == null) CreateComponent() approach.

This PR modernizes it to use ComponentDefault and modernizes the accompanying tutorial as well.

I've compile- and run-tested this change and it seems everything works as it should.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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