review-comment: Synchronize when serializing SentryNetworkDetails for breadcrumb

#7588 (comment)

Prevent SentryNetworkDetailsData#serialize from reading properties that may be
mutated concurrently by SentryNetworkDetailsData#setResponse

setState
 - calls serialize when newState == .completed
completionHandler
 - calls setResponse when invoked.

in testing, the completionHandler is invoked after setState(.completed)
returns. However based on research this is not guaranteed so lock so ensure
no concurrent modification of SentryNetworkDetailsData

Author: 43jay

Sources/Sentry/SentryNetworkTracker.m

@@ -481,12 +481,14 @@ - (void)addBreadcrumbForSessionTask:(NSURLSessionTask *)sessionTask
     }
 
 #if SENTRY_TARGET_REPLAY_SUPPORTED
-    // Add network details if available
-    SentryReplayNetworkDetails *networkDetails
-        = objc_getAssociatedObject(sessionTask, &SentryNetworkDetailsKey);
-    if (networkDetails) {
-        breadcrumbData[SentryReplayNetworkDetails.replayNetworkDetailsKey] =
-            [networkDetails serialize];
+    // Check if network details was enabled for this url.
+    @synchronized(sessionTask) {
+        SentryReplayNetworkDetails *networkDetails
+            = objc_getAssociatedObject(sessionTask, &SentryNetworkDetailsKey);
+        if (networkDetails) {
+            breadcrumbData[SentryReplayNetworkDetails.replayNetworkDetailsKey] =
+                [networkDetails serialize];
+        }
     }
 #endif // SENTRY_TARGET_REPLAY_SUPPORTED