[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/TankDrive/robot.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+#
+# 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 wpilib
+
+
+class MyRobot(wpilib.TimedRobot):
+    """
+    This is a demo program showing the use of the DifferentialDrive class.
+    Runs the motors with tank steering.
+    """
+
+    def __init__(self):
+        """Robot initialization function"""
+        super().__init__()
+
+        leftMotor = wpilib.PWMSparkMax(0)
+        rightMotor = wpilib.PWMSparkMax(1)
+        self.robotDrive = wpilib.DifferentialDrive(leftMotor, rightMotor)
+        self.leftStick = wpilib.Joystick(0)
+        self.rightStick = wpilib.Joystick(1)
+
+        # We need to invert one side of the drivetrain so that positive voltages
+        # result in both sides moving forward. Depending on how your robot's
+        # gearbox is constructed, you might have to invert the left side instead.
+        rightMotor.setInverted(True)
+
+    def teleopPeriodic(self):
+        self.robotDrive.tankDrive(-self.leftStick.getY(), -self.rightStick.getY())