[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/ArmSimulation/constants.py

@@ -0,0 +1,33 @@
+#
+# 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
+
+from wpimath import units
+
+
+class Constants:
+    kMotorPort = 0
+    kEncoderAChannel = 0
+    kEncoderBChannel = 1
+    kJoystickPort = 0
+
+    kArmPositionKey = "ArmPosition"
+    kArmPKey = "ArmP"
+
+    # The P gain for the PID controller that drives this arm.
+    kDefaultArmKp = 50.0
+    kDefaultArmSetpointDegrees = 75.0
+
+    # distance per pulse = (angle per revolution) / (pulses per revolution)
+    #  = (2 * PI rads) / (4096 pulses)
+    kArmEncoderDistPerPulse = 2.0 * math.pi / 4096
+
+    kArmReduction = 200
+    kArmMass = 8.0  # Kilograms
+    kArmLength = units.inchesToMeters(30)
+    kMinAngleRads = units.degreesToRadians(-75)
+    kMaxAngleRads = units.degreesToRadians(255)