[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/snippets/IntermediateVision/vision.py

@@ -0,0 +1,53 @@
+#
+# 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.
+#
+
+#
+# This is a demo program showing the use of OpenCV to do vision processing. The image is acquired
+# from the USB camera, then a rectangle is put on the image and sent to the dashboard. OpenCV has
+# many methods for different types of processing.
+#
+# NOTE: This code runs in its own process, so we cannot access the robot here,
+#       nor can we create/use/see wpilib objects
+#
+# To try this code out locally (if you have robotpy-cscore installed), you
+# can execute `python3 -m cscore vision.py:main`
+#
+
+import cv2
+import numpy as np
+
+from cscore import CameraServer as CS
+
+
+def main():
+    # Get the UsbCamera from CameraServer
+    camera = CS.startAutomaticCapture()
+    # Set the resolution
+    camera.setResolution(640, 480)
+
+    # Get a CvSink. This will capture images from the camera
+    cvSink = CS.getVideo()
+    # Setup a CvSource. This will send images back to the Dashboard
+    outputStream = CS.putVideo("Rectangle", 640, 480)
+
+    # Mats are very memory expensive. Lets reuse this Mat.
+    mat = np.zeros(shape=(480, 640, 3), dtype=np.uint8)
+
+    while True:
+        # Tell the CvSink to grab a frame from the camera and put it
+        # in the source image.  If there is an error notify the output.
+        time, mat = cvSink.grabFrame(mat)
+        if time == 0:
+            # Send the output the error.
+            outputStream.notifyError(cvSink.getError())
+            # skip the rest of the current iteration
+            continue
+
+        # Put a rectangle on the image
+        cv2.rectangle(mat, (100, 100), (400, 400), (255, 255, 255), 5)
+
+        # Give the output stream a new image to display
+        outputStream.putFrame(mat)