Restructure Netty tests for modules

Move tests outside of io.netty.buffer package because that causes a conflict
with Netty's modules. Change functions marked as protected that are used in
tests to be public to facilitate this refactoring.

java/memory/memory-netty-buffer-patch/src/main/java/io/netty/buffer/NettyArrowBuf.java

@@ -436,7 +436,8 @@ public byte getByte(int index) {
   }
 
   @Override
-  protected short _getShortLE(int index) {
+  @VisibleForTesting
+  public short _getShortLE(int index) {
     short s = getShort(index);
     return Short.reverseBytes(s);
   }
@@ -452,7 +453,8 @@ public short getShort(int index) {
   }
 
   @Override
-  protected int _getIntLE(int index) {
+  @VisibleForTesting
+  public int _getIntLE(int index) {
     int value = getInt(index);
     return Integer.reverseBytes(value);
   }
@@ -468,7 +470,8 @@ public int getInt(int index) {
   }
 
   @Override
-  protected long _getLongLE(int index) {
+  @VisibleForTesting
+  public long _getLongLE(int index) {
     long value = getLong(index);
     return Long.reverseBytes(value);
   }
@@ -509,7 +512,8 @@ protected void _setShortLE(int index, int value) {
   }
 
   @Override
-  protected void _setShort(int index, int value) {
+  @VisibleForTesting
+  public void _setShort(int index, int value) {
     setShort(index, value);
   }
 
@@ -581,7 +585,7 @@ public NettyArrowBuf setMedium(int index, int value) {
 
   @Override
   @VisibleForTesting
-  protected void _setInt(int index, int value) {
+  public void _setInt(int index, int value) {
     setInt(index, value);
   }
 
@@ -599,7 +603,8 @@ public NettyArrowBuf setInt(int index, int value) {
   }
 
   @Override
-  protected void _setLong(int index, long value) {
+  @VisibleForTesting
+  public void _setLong(int index, long value) {
     setLong(index, value);
   }
 

java/memory/memory-netty/src/test/java/io/netty/buffer/TestExpandableByteBuf.java → java/memory/memory-netty/src/test/java/org/apache/arrow/io/netty/buffer/TestExpandableByteBuf.java

@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-package io.netty.buffer;
+package org.apache.arrow.io.netty.buffer;
 
 import org.apache.arrow.memory.ArrowBuf;
 import org.apache.arrow.memory.BufferAllocator;

java/memory/memory-netty/src/test/java/io/netty/buffer/TestNettyArrowBuf.java → java/memory/memory-netty/src/test/java/org/apache/arrow/io/netty/buffer/TestNettyArrowBuf.java

@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-package io.netty.buffer;
+package org.apache.arrow.io.netty.buffer;
 
 import java.nio.ByteBuffer;