FR3 Interface

[alberthli]

This PR adds the FR3 hardware interface (ARM ONLY).

BREAKING:

• The setup scripts were changed so that unitree deps are now OPT-IN like all other hardware dep groups

TODOs for this PR:

• Update the instructions in the quickstart to include unitree setup
• Write an example controller that flushes this pipe for the two cases: joint control and ee pose control
• Write the corresponding sim interface + add the relevant models. for the case of ee pose control, we're going to need some sort of IK interface to connect with mujoco, e.g. mink

TODOs for future PRs:

• Handle the gripper in the FR3 interface (or don't? maybe handle this in a follow-up PR once the 2F-140 has been integrated)
• Create a downstream project that depends on the obelisk stuff but with all the FR3 control infrastructure in it