[wpimath] Replace Speeds with Velocities (#8479)

I left "free speed" alone since that's the technical term for it. In
general, velocity is a vector quantity, and speed is a magnitude (i.e.,
a strictly positive value).

This PR also replaces the speed verbiage in MotorController with duty
cycle.

Fixes #8423.

robotpyExamples/RapidReactCommandBot/constants.py

@@ -63,10 +63,10 @@ class ShooterConstants:
     # On a real robot the feedforward constants should be empirically determined; these are
     # reasonable guesses.
     kS = 0.05  # V
-    # Should have value 12V at free speed
+    # Should have value 12V at free velocity
     kV = 12.0 / kShooterFreeRPS  # V/(rot/s)
 
-    kFeederSpeed = 0.5
+    kFeederVelocity = 0.5
 
 
 class IntakeConstants:
@@ -82,7 +82,7 @@ class StorageConstants:
 class AutoConstants:
     kTimeout = 3
     kDriveDistance = 2.0  # m
-    kDriveSpeed = 0.5
+    kDriveVelocity = 0.5
 
 
 class OIConstants:

robotpyExamples/RapidReactCommandBot/rapidreactcommandbot.py

@@ -82,7 +82,7 @@ class RapidReactCommandBot:
 
         Scheduled during :meth:`.Robot.autonomousInit`.
         """
-        # Drive forward for 2 meters at half speed with a 3 second timeout
+        # Drive forward for 2 meters at half velocity with a 3 second timeout
         return self.drive.driveDistanceCommand(
-            AutoConstants.kDriveDistance, AutoConstants.kDriveSpeed
+            AutoConstants.kDriveDistance, AutoConstants.kDriveVelocity
         ).withTimeout(AutoConstants.kTimeout)

robotpyExamples/RapidReactCommandBot/subsystems/drive.py

@@ -91,12 +91,12 @@ class Drive(Subsystem):
             "arcadeDrive"
         )
 
-    def driveDistanceCommand(self, distance: float, speed: float) -> Command:
+    def driveDistanceCommand(self, distance: float, velocity: float) -> Command:
         """Returns a command that drives the robot forward a specified distance at a specified
-        speed.
+        velocity.
 
         :param distance: The distance to drive forward in meters
-        :param speed: The fraction of max speed at which to drive
+        :param velocity: The fraction of max velocity at which to drive
         """
         return (
             self.runOnce(
@@ -105,7 +105,7 @@ class Drive(Subsystem):
                     self.rightEncoder.reset(),
                 )
             )
-            .andThen(self.run(lambda: self.drive.arcadeDrive(speed, 0)))
+            .andThen(self.run(lambda: self.drive.arcadeDrive(velocity, 0)))
             .until(
                 lambda: max(
                     self.leftEncoder.getDistance(), self.rightEncoder.getDistance()