Suppress AccessController deprecation warning for Java 17+ (#682)

* Suppress AccessController deprecation warning

AccessController has been deprecated for removal since Java 17 as part of JEP 411.
Since snappy-java needs to maintain compatibility with Java 8+, we cannot remove
the AccessController.doPrivileged calls. This commit adds @SuppressWarnings("removal")
to suppress the deprecation warning while maintaining backward compatibility.

The AccessController calls are used to bypass SecurityManager restrictions when
cleaning DirectByteBuffers. In Java 17+, these calls effectively just run the
action directly since SecurityManager is being phased out.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

* Apply @SuppressWarnings to specific methods instead of class level

Based on review feedback, narrowed the scope of @SuppressWarnings("removal")
annotations to only the specific methods and code blocks that use AccessController,
rather than applying it at the class level. This approach:

- Reduces the scope of the suppression
- Avoids hiding other potential deprecation warnings
- Follows best practices for targeted warning suppression

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

---------

Co-authored-by: Claude <[email protected]>

Author: xerial

src/main/java/org/xerial/snappy/pool/DirectByteBuffers.java

@@ -35,6 +35,7 @@ final class DirectByteBuffers {
         // and https://github.com/apache/lucene-solr/blob/7e03427fa14a024ce257babcb8362d2451941e21/lucene/core/src/java/org/apache/lucene/store/MMapDirectory.java
         MethodHandle cleanHandle = null;
         try {
+            @SuppressWarnings("removal")  // AccessController is deprecated for removal in Java 17+
             final PrivilegedExceptionAction<MethodHandle> action = new PrivilegedExceptionAction<MethodHandle>() {
 
                 @Override
@@ -90,7 +91,9 @@ public MethodHandle run() throws Exception {
                 }
             };
 
-            cleanHandle = AccessController.doPrivileged(action);
+            @SuppressWarnings("removal")  // AccessController is deprecated for removal in Java 17+
+            MethodHandle temp = AccessController.doPrivileged(action);
+            cleanHandle = temp;
 
         } catch (Throwable t) {
             Logger.getLogger(DirectByteBuffers.class.getName()).log(Level.FINE, "Exception occurred attempting to lookup Sun specific DirectByteBuffer cleaner classes.", t);
@@ -121,6 +124,7 @@ static boolean nonNull(Object o) {
      *
      * @param buffer The {@code ByteBuffer} to release. Must not be {@code null}. Must be  {@link ByteBuffer#isDirect() direct}.
      */
+    @SuppressWarnings("removal")  // AccessController is deprecated for removal in Java 17+
     public static void releaseDirectByteBuffer(final ByteBuffer buffer)
     {
         assert buffer != null && buffer.isDirect();