[robotpy][examples] Split examples and snippets (#8944)

This also updates the bazel scripts to behave more like the C++ and Java
examples, and updates the copybara scripts to be able to sync up
`mostrobotpy`

robotpyExamples/examples/ElevatorExponentialSimulation/subsystems/elevator.py

@@ -0,0 +1,134 @@
+#
+# Copyright (c) FIRST and other WPILib contributors.
+# Open Source Software; you can modify and/or share it under the terms of
+# the WPILib BSD license file in the root directory of this project.
+#
+
+import wpilib
+import wpilib.simulation
+import wpimath
+import wpimath.units
+
+import constants
+
+
+class Elevator:
+    def __init__(self) -> None:
+        # This gearbox represents a gearbox containing 4 Vex 775pro motors.
+        self.elevatorGearbox = wpimath.DCMotor.NEO(2)
+
+        self.profile = wpimath.ExponentialProfileMeterVolts(
+            wpimath.ExponentialProfileMeterVolts.Constraints.fromCharacteristics(
+                constants.kElevatorMaxV,
+                constants.kElevatorkV,
+                constants.kElevatorkA,
+            )
+        )
+
+        self.setpoint = wpimath.ExponentialProfileMeterVolts.State(0, 0)
+
+        # Standard classes for controlling our elevator
+        self.pidController = wpimath.PIDController(
+            constants.kElevatorKp, constants.kElevatorKi, constants.kElevatorKd
+        )
+
+        self.feedforward = wpimath.ElevatorFeedforward(
+            constants.kElevatorkS,
+            constants.kElevatorkG,
+            constants.kElevatorkV,
+            constants.kElevatorkA,
+        )
+        self.encoder = wpilib.Encoder(
+            constants.kEncoderAChannel, constants.kEncoderBChannel
+        )
+        self.motor = wpilib.PWMSparkMax(constants.kMotorPort)
+
+        # Simulation classes help us simulate what's going on, including gravity.
+        self.elevatorSim = wpilib.simulation.ElevatorSim(
+            self.elevatorGearbox,
+            constants.kElevatorGearing,
+            constants.kCarriageMass,
+            constants.kElevatorDrumRadius,
+            constants.kMinElevatorHeight,
+            constants.kMaxElevatorHeight,
+            True,
+            0,
+            [0.005, 0.0],
+        )
+        self.encoderSim = wpilib.simulation.EncoderSim(self.encoder)
+        self.motorSim = wpilib.simulation.PWMMotorControllerSim(self.motor)
+
+        # Create a Mechanism2d visualization of the elevator
+        self.mech2d = wpilib.Mechanism2d(
+            wpimath.units.inchesToMeters(10),
+            wpimath.units.inchesToMeters(51),
+        )
+        self.mech2dRoot = self.mech2d.getRoot(
+            "Elevator Root",
+            wpimath.units.inchesToMeters(5),
+            wpimath.units.inchesToMeters(0.5),
+        )
+        self.elevatorMech2d = self.mech2dRoot.appendLigament(
+            "Elevator", self.elevatorSim.getPosition(), 90
+        )
+
+        # Subsystem constructor.
+        self.encoder.setDistancePerPulse(constants.kElevatorEncoderDistPerPulse)
+
+        # Publish Mechanism2d to SmartDashboard
+        # To view the Elevator visualization, select Network Tables -> SmartDashboard -> Elevator Sim
+        wpilib.SmartDashboard.putData("Elevator Sim", self.mech2d)
+
+    def simulationPeriodic(self) -> None:
+        """Advance the simulation."""
+        # In this method, we update our simulation of what our elevator is doing
+        # First, we set our "inputs" (voltages)
+        self.elevatorSim.setInputVoltage(
+            self.motorSim.getThrottle() * wpilib.RobotController.getBatteryVoltage()
+        )
+
+        # Next, we update it. The standard loop time is 20ms.
+        self.elevatorSim.update(0.020)
+
+        # Finally, we set our simulated encoder's readings and simulated battery voltage
+        self.encoderSim.setDistance(self.elevatorSim.getPosition())
+        # SimBattery estimates loaded battery voltages
+        wpilib.simulation.RoboRioSim.setVInVoltage(
+            wpilib.simulation.BatterySim.calculate([self.elevatorSim.getCurrentDraw()])
+        )
+
+    def reachGoal(self, goal: float) -> None:
+        """Run control loop to reach and maintain goal.
+
+        :param goal: the position to maintain
+        """
+        goalState = wpimath.ExponentialProfileMeterVolts.State(goal, 0)
+
+        next_state = self.profile.calculate(0.020, self.setpoint, goalState)
+
+        # With the setpoint value we run PID control like normal
+        pidOutput = self.pidController.calculate(
+            self.encoder.getDistance(), self.setpoint.position
+        )
+        feedforwardOutput = self.feedforward.calculate(
+            self.setpoint.velocity, next_state.velocity
+        )
+
+        self.motor.setVoltage(pidOutput + feedforwardOutput)
+
+        self.setpoint = next_state
+
+    def stop(self) -> None:
+        """Stop the control loop and motor output."""
+        self.motor.setThrottle(0.0)
+
+    def reset(self) -> None:
+        """Reset Exponential profile to begin from current position on enable."""
+        self.setpoint = wpimath.ExponentialProfileMeterVolts.State(
+            self.encoder.getDistance(), 0
+        )
+
+    def updateTelemetry(self) -> None:
+        """Update telemetry, including the mechanism visualization."""
+        # Update elevator visualization with position
+        self.elevatorMech2d.setLength(self.encoder.getDistance())