Use wpi::span instead of wpi::ArrayRef across all libraries (#3414)

- Remove ArrayRef.h
- Add SpanExtras.h for a couple of convenience functions

wpilibc/src/main/native/include/frc/AddressableLED.h

@@ -9,7 +9,7 @@
 #include <hal/AddressableLEDTypes.h>
 #include <hal/Types.h>
 #include <units/time.h>
-#include <wpi/ArrayRef.h>
+#include <wpi/span.h>
 
 #include "util/Color.h"
 #include "util/Color8Bit.h"
@@ -107,7 +107,7 @@ class AddressableLED {
    *
    * @param ledData the buffer to write
    */
-  void SetData(wpi::ArrayRef<LEDData> ledData);
+  void SetData(wpi::span<const LEDData> ledData);
 
   /**
    * Sets the led output data.