GH-825: Add UUID canonical extension type (#903)

Author: jhrotko

vector/src/main/java/org/apache/arrow/vector/BaseFixedWidthVector.java

@@ -70,6 +70,7 @@ public BaseFixedWidthVector(Field field, final BufferAllocator allocator, final
     refreshValueCapacity();
   }
 
+  @Override
   public int getTypeWidth() {
     return typeWidth;
   }

vector/src/main/java/org/apache/arrow/vector/FixedWidthVector.java

@@ -31,4 +31,7 @@ public interface FixedWidthVector extends ElementAddressableVector {
 
   /** Zero out the underlying buffer backing this vector. */
   void zeroVector();
+
+  /** Get the width of the type in bytes. */
+  int getTypeWidth();
 }