[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/commands/arcadedrive.py

@@ -0,0 +1,34 @@
+#
+# 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 typing
+import commands2
+from subsystems.drivetrain import Drivetrain
+
+
+class ArcadeDrive(commands2.Command):
+    def __init__(
+        self,
+        drive: Drivetrain,
+        xaxisVelocitySupplier: typing.Callable[[], float],
+        zaxisRotateSupplier: typing.Callable[[], float],
+    ) -> None:
+        """Creates a new ArcadeDrive. This command will drive your robot according to the velocity supplier
+        lambdas. This command does not terminate.
+
+        :param drivetrain:  The drivetrain subsystem on which this command will run
+        :param xaxisVelocitySupplier:     Callable supplier of forward/backward velocity
+        :param zaxisRotateSupplier:       Callable supplier of rotational velocity
+        """
+
+        self.drive = drive
+        self.xaxisVelocitySupplier = xaxisVelocitySupplier
+        self.zaxisRotateSupplier = zaxisRotateSupplier
+
+        self.addRequirements(self.drive)
+
+    def execute(self) -> None:
+        self.drive.arcadeDrive(self.xaxisVelocitySupplier(), self.zaxisRotateSupplier())