fix(core): Avoid KeySetView in context serialization

Use ConcurrentHashMap.keys() when creating sorted context key snapshots so the serialization path stays compatible with Android API 21. Keep the array snapshot optimization without relying on KeySetView, which AnimalSniffer rejects for the SDK's minSdk.

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

Author: adinauer

sentry/api/sentry.api

@@ -7619,6 +7619,7 @@ public final class io/sentry/util/CollectionUtils {
 	public static fun newHashMap (Ljava/util/Map;)Ljava/util/Map;
 	public static fun reverseListIterator (Ljava/util/concurrent/CopyOnWriteArrayList;)Ljava/util/ListIterator;
 	public static fun size (Ljava/lang/Iterable;)I
+	public static fun toSortedStringArray (Ljava/util/Enumeration;I)[Ljava/lang/String;
 }
 
 public abstract interface class io/sentry/util/CollectionUtils$Mapper {

sentry/src/main/java/io/sentry/MonitorContexts.java

@@ -1,17 +1,16 @@
 package io.sentry;
 
+import io.sentry.util.CollectionUtils;
 import io.sentry.util.Objects;
 import io.sentry.vendor.gson.stream.JsonToken;
 import java.io.IOException;
-import java.util.Arrays;
 import java.util.concurrent.ConcurrentHashMap;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 public final class MonitorContexts extends ConcurrentHashMap<String, Object>
     implements JsonSerializable {
   private static final long serialVersionUID = 3987329379811822556L;
-  private static final String[] EMPTY_KEYS = new String[0];
 
   public MonitorContexts() {}
 
@@ -49,8 +48,7 @@ public void serialize(final @NotNull ObjectWriter writer, final @NotNull ILogger
       throws IOException {
     writer.beginObject();
     // Serialize in alphabetical order to keep determinism.
-    final String[] sortedKeys = keySet().toArray(EMPTY_KEYS);
-    Arrays.sort(sortedKeys);
+    final String[] sortedKeys = CollectionUtils.toSortedStringArray(keys(), size());
     for (final String key : sortedKeys) {
       final Object value = get(key);
       if (value != null) {

sentry/src/main/java/io/sentry/protocol/Contexts.java

@@ -10,11 +10,11 @@
 import io.sentry.ProfileContext;
 import io.sentry.SpanContext;
 import io.sentry.util.AutoClosableReentrantLock;
+import io.sentry.util.CollectionUtils;
 import io.sentry.util.HintUtils;
 import io.sentry.util.Objects;
 import io.sentry.vendor.gson.stream.JsonToken;
 import java.io.IOException;
-import java.util.Arrays;
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.Map;
@@ -27,7 +27,6 @@
 public class Contexts implements JsonSerializable {
   private static final long serialVersionUID = 252445813254943011L;
   public static final String REPLAY_ID = "replay_id";
-  private static final String[] EMPTY_KEYS = new String[0];
 
   private final @NotNull ConcurrentHashMap<String, Object> internalStorage =
       new ConcurrentHashMap<>();
@@ -302,8 +301,7 @@ public void serialize(final @NotNull ObjectWriter writer, final @NotNull ILogger
       throws IOException {
     writer.beginObject();
     // Serialize in alphabetical order to keep determinism.
-    final String[] sortedKeys = internalStorage.keySet().toArray(EMPTY_KEYS);
-    Arrays.sort(sortedKeys);
+    final String[] sortedKeys = CollectionUtils.toSortedStringArray(keys(), internalStorage.size());
     for (final String key : sortedKeys) {
       final Object value = get(key);
       if (value != null) {

sentry/src/main/java/io/sentry/util/CollectionUtils.java

@@ -1,7 +1,9 @@
 package io.sentry.util;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
+import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.List;
 import java.util.ListIterator;
@@ -15,9 +17,28 @@
 /** Util class for Collections */
 @ApiStatus.Internal
 public final class CollectionUtils {
+  private static final String[] EMPTY_STRINGS = new String[0];
 
   private CollectionUtils() {}
 
+  public static @NotNull String[] toSortedStringArray(
+      final @NotNull Enumeration<String> source, final int size) {
+    String[] sorted = size == 0 ? EMPTY_STRINGS : new String[size];
+    int index = 0;
+    while (source.hasMoreElements()) {
+      if (index == sorted.length) {
+        sorted = Arrays.copyOf(sorted, sorted.length + 1);
+      }
+      sorted[index] = source.nextElement();
+      index++;
+    }
+    if (index != sorted.length) {
+      sorted = Arrays.copyOf(sorted, index);
+    }
+    Arrays.sort(sorted);
+    return sorted;
+  }
+
   /**
    * Returns an Iterator size
    *