Restore final keyword to remaining package-private classes

Author: trask

disk-buffering/src/main/java/io/opentelemetry/contrib/disk/buffering/exporters/NoopExporterCallback.java

@@ -8,7 +8,7 @@
 import io.opentelemetry.contrib.disk.buffering.SignalType;
 import javax.annotation.Nullable;
 
-class NoopExporterCallback implements ExporterCallback {
+final class NoopExporterCallback implements ExporterCallback {
   static final NoopExporterCallback INSTANCE = new NoopExporterCallback();
 
   private NoopExporterCallback() {}

disk-buffering/src/main/java/io/opentelemetry/contrib/disk/buffering/exporters/SignalStorageExporter.java

@@ -18,7 +18,7 @@
 import java.util.concurrent.TimeoutException;
 
 /** Internal utility for common export to disk operations across all exporters. */
-class SignalStorageExporter<T> {
+final class SignalStorageExporter<T> {
   private final SignalStorage<T> storage;
   private final ExporterCallback callback;
   private final Duration writeTimeout;

disk-buffering/src/main/java/io/opentelemetry/contrib/disk/buffering/storage/result/DefaultWriteResult.java

@@ -7,7 +7,7 @@
 
 import javax.annotation.Nullable;
 
-class DefaultWriteResult implements WriteResult {
+final class DefaultWriteResult implements WriteResult {
   private final boolean successful;
   @Nullable private final Throwable error;