[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/constants.py

@@ -0,0 +1,38 @@
+#
+# 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 math
+
+import wpimath.units
+
+kMotorPort = 0
+kEncoderAChannel = 0
+kEncoderBChannel = 1
+kJoystickPort = 0
+
+kElevatorKp = 0.75
+kElevatorKi = 0.0
+kElevatorKd = 0.0
+
+kElevatorMaxV = 10.0  # volts (V)
+kElevatorkS = 0.0  # volts (V)
+kElevatorkG = 0.62  # volts (V)
+kElevatorkV = 3.9  # volts (V)
+kElevatorkA = 0.06  # volts (V)
+
+kElevatorGearing = 5.0
+kElevatorDrumRadius = wpimath.units.inchesToMeters(1.0)
+kCarriageMass = wpimath.units.lbsToKilograms(12)  # kg
+
+kSetpoint = wpimath.units.inchesToMeters(42.875)
+kLowerkSetpoint = wpimath.units.inchesToMeters(15)
+# Encoder is reset to measure 0 at the bottom, so minimum height is 0.
+kMinElevatorHeight = 0.0  # m
+kMaxElevatorHeight = wpimath.units.inchesToMeters(50)
+
+# distance per pulse = (distance per revolution) / (pulses per revolution)
+#  = (Pi * D) / ppr
+kElevatorEncoderDistPerPulse = 2.0 * math.pi * kElevatorDrumRadius / 4096