Impedance settings in joints.py have mixed real and non-dim inputs

[tkevinbest]

🚀 Feature Request

The set_joint_impedance method and others require both the output impedance and the current control gains to be specified. The output impedance is in real units whereas the current control gains are in arbitrary dephy units. I think these commands should be separated to maintain the hardware abstraction functionality.

I think we should move setting any current control gains to its own method and if the user wants to change those, they need to call that method. Setting the joint impedance should be independent of the current control gains. Under the hood (because I know Flexsea requires us to send both impedance and current control gains together), we should keep track of the latest current control gains and just handle adding those in for the user.