[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/UnitTest/constants.py

@@ -0,0 +1,16 @@
+#
+# 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.
+#
+
+
+class IntakeConstants:
+    MOTOR_PORT = 1
+
+    PISTON_FWD_CHANNEL = 0
+    PISTON_REV_CHANNEL = 1
+    INTAKE_VELOCITY = 0.5
+
+
+JOYSTICK_INDEX = 0