feat: Add ensureNoCircularStructures experiment to help debug serialization bugs (#3776)

Author: kamilogorek

packages/core/src/baseclient.ts

@@ -389,6 +389,12 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
       // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
       normalized.contexts.trace = event.contexts.trace;
     }
+
+    const { _experiments = {} } = this.getOptions();
+    if (_experiments.ensureNoCircularStructures) {
+      return normalize(normalized);
+    }
+
     return normalized;
   }