[Spinal] Improve the process of servo bridge

[tongtybj]

What is this

Improve the servo bridge process between spinal (spinal_ros_bridge) and ros system.

• introduce common ros topics (servo states from spinal: servo/states, servo command to spinal: servo/target_states) shared in different servo groups (e.g., joint, gimbal)
• classify servo (servo group) into three types:
  • a) servo that shares the common topics (e.g. joint, gimbal with version after 1.3.0);
  • b) servo that has no real state from spinal (e.g. gimbal with version before 1.3.0);
  • c) servo that has different topics (e.g. small servo for extra actuator), use boolean flag no_real_state.

Details

Recently servo bridge process has a critical conflict/duplication between groups that uses same ros topics between servo_bridge and spinal_ros_bridge. This causes the failure for model that has vectoring actuators other than joints (e.g. dragon, hydrus_xi). This PR solves this conflict by introducing the common ros topics for all servo group.

[tongtybj]

This is the complete work based on https://github.com/tongtybj/aerial_robot/commit/4c1de3ea0118e9c0685a6b438cdc75ab2027fccd

[tongtybj]

@greenpepper123

Could we test this PR with hydrus_xi when you are available?

[tongtybj]

Have checked with Dragon