[Feature-Request] {Pipeline generation as a plugin}

[Serafadam]

Start with the why:

Currently for custom devices (FFC) users can use "CamArray" option in depthai_ros_driver but for now it doesn't have the option for custom NN/Stereo setups in that scenario.

Move to the what:

Adding an option to use ROS plugin for pipeline construction, so that we keep dynamic parameters for sensors, and can instead write pipelines the simpler way.

Move to the how:

Change pipeline_generator so that current Pipeline options are defined as plugins and loaded in runtime. Each plugin only needs to return daiNodes vector.