Make UnpooledHeapByteBuf array methods protected (#8015)

Motivation:

Currently there is not a clear way to provide a byte array to a netty
ByteBuf and be informed when it is released. This is a would be a
valuable addition for projects that integrate with netty but also pool
their own byte arrays.

Modification:

Modified the UnpooledHeapByteBuf class so that the freeArray method is
protected visibility instead of default. This will allow a user to
subclass the UnpooledHeapByteBuf, provide a byte array, and override
freeArray to return the byte array to a pool when it is called.
Additionally this makes this implementation equivalent to
UnpooledDirectByteBuf (freeDirect is protected).

Additionally allocateArray is also made protect to provide another override
option for subclasses.

Result:

Users can override UnpooledHeapByteBuf#freeArray and
UnpooledHeapByteBuf#allocateArray.

buffer/src/main/java/io/netty/buffer/UnpooledByteBufAllocator.java

@@ -140,14 +140,14 @@ public final class UnpooledByteBufAllocator extends AbstractByteBufAllocator imp
         }
 
         @Override
-        byte[] allocateArray(int initialCapacity) {
+        protected byte[] allocateArray(int initialCapacity) {
             byte[] bytes = super.allocateArray(initialCapacity);
             ((UnpooledByteBufAllocator) alloc()).incrementHeap(bytes.length);
             return bytes;
         }
 
         @Override
-        void freeArray(byte[] array) {
+        protected void freeArray(byte[] array) {
             int length = array.length;
             super.freeArray(array);
             ((UnpooledByteBufAllocator) alloc()).decrementHeap(length);
@@ -160,14 +160,14 @@ public final class UnpooledByteBufAllocator extends AbstractByteBufAllocator imp
         }
 
         @Override
-        byte[] allocateArray(int initialCapacity) {
+        protected byte[] allocateArray(int initialCapacity) {
             byte[] bytes = super.allocateArray(initialCapacity);
             ((UnpooledByteBufAllocator) alloc()).incrementHeap(bytes.length);
             return bytes;
         }
 
         @Override
-        void freeArray(byte[] array) {
+        protected void freeArray(byte[] array) {
             int length = array.length;
             super.freeArray(array);
             ((UnpooledByteBufAllocator) alloc()).decrementHeap(length);

buffer/src/main/java/io/netty/buffer/UnpooledHeapByteBuf.java

@@ -84,11 +84,11 @@ public class UnpooledHeapByteBuf extends AbstractReferenceCountedByteBuf {
         setIndex(0, initialArray.length);
     }
 
-    byte[] allocateArray(int initialCapacity) {
+    protected byte[] allocateArray(int initialCapacity) {
         return new byte[initialCapacity];
     }
 
-    void freeArray(byte[] array) {
+    protected void freeArray(byte[] array) {
         // NOOP
     }
 

buffer/src/main/java/io/netty/buffer/UnpooledUnsafeHeapByteBuf.java

@@ -30,7 +30,7 @@ class UnpooledUnsafeHeapByteBuf extends UnpooledHeapByteBuf {
     }
 
     @Override
-    byte[] allocateArray(int initialCapacity) {
+    protected byte[] allocateArray(int initialCapacity) {
         return PlatformDependent.allocateUninitializedArray(initialCapacity);
     }