[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/XrpReference/subsystems/arm.py

@@ -0,0 +1,28 @@
+#
+# 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 commands2
+import xrp
+
+
+class Arm(commands2.Subsystem):
+
+    def __init__(self):
+        """Creates a new Arm."""
+
+        # Device number 4 maps to the physical Servo 1 port on the XRP
+        self.armServo = xrp.XRPServo(4)
+
+    def periodic(self):
+        """This method will be called once per scheduler run"""
+
+    def setAngle(self, angleDeg: float):
+        """
+        Set the current angle of the arm (0 - 180 degrees).
+
+        :param angleDeg: Desired arm angle in degrees
+        """
+        self.armServo.setAngle(angleDeg)