ref(core): Use primitive long for EventProcessorAndOrder.order

Avoid boxing by storing the order as a primitive long instead of a
boxed Long. The constructor already normalizes a null order to
System.nanoTime(), so the field never needs to represent null.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: runningcode

sentry/src/main/java/io/sentry/internal/eventprocessor/EventProcessorAndOrder.java

@@ -7,7 +7,7 @@
 public final class EventProcessorAndOrder implements Comparable<EventProcessorAndOrder> {
 
   private final @NotNull EventProcessor eventProcessor;
-  private final @NotNull Long order;
+  private final long order;
 
   public EventProcessorAndOrder(
       final @NotNull EventProcessor eventProcessor, final @Nullable Long order) {