Upgrade step and reset pipelines to proper pipelines with named functions

[amacati]

Named, ordered simulation pipelines

Replaces the ad-hoc tuples of functions in sim.step_pipeline/sim.reset_pipeline with a Pipeline type: an ordered collection of named functions. Stages are addressed by name instead of by position, so you can splice in disturbances, randomization etc at a precise point without counting indices.

Stage names default to fn.__name__ and must be unique. Pass name= for anonymous callables (e.g. functools.partial). Iterating a pipeline yields the functions in order.

Usage

Pipelines are easier to inspect:

from crazyflow.sim import Sim
from crazyflow.sim.data import SimData

sim = Sim()

print(sim.step_pipeline)                # Pipeline(step_attitude_controller -> ... -> clip_floor_pos)
sim.step_pipeline.names                 # ordered stage names
"integration" in sim.step_pipeline      # True
sim.step_pipeline.index("integration")  # position of a stage
sim.step_pipeline["clip_floor_pos"]     # look up a stage's function by name
len(sim.step_pipeline)                  # number of stages

Inserting new functions also becomes easier with named access:

def disturbance(data: SimData) -> SimData:
    return data.replace(states=data.states.replace(vel=data.states.vel + 1e-5))

def monitor(data: SimData) -> SimData:
    return data

sim.step_pipeline.insert_before("integration", disturbance)
sim.step_pipeline.insert_after("integration", monitor)
sim.step_pipeline.prepend(monitor, name="pre_monitor")          # name= for a reused callable
sim.step_pipeline.replace("clip_floor_pos", lambda data: data)  # swap impl, keep name + position
sim.step_pipeline.remove("monitor")

We also allow some syntactic sugar to make common operations like appending easier

sim.step_pipeline = sim.step_pipeline + monitor  # Same as append with __name__
sim.step_pipeline.extend(some_other_pipeline)    # Adding multiple steps at once
for stage in sim.step_pipeline:                  # iterating yields the functions, in order
    ...

Pipelines also expose append / keys() / values() / items() and __repr__for nicer prints.

Notes:

• + and construction accept functions or pipelines only. Use append / insert_* with name= for explicit names.
• replace / remove raise on unknown names. Duplicate names raise on insert.

Closes #64

[ratheron]

Looks very nice! I have two comments on the implementation

[ratheron]

The controller has clippings as well. Maybe we should add a note that either we remove the clipping or we start at a certain height.

[ratheron]

Maybe this should be a separate reset step, in case we want to remove it? Right now, the reset pipeline appears to be empty, even though the data is reset to the default data.

[amacati]

Closed in favor of #68