4.2.0 release notes updates

Author: michaelklishin

release-notes/4.2.0.md

@@ -184,6 +184,18 @@ This section is **incomplete** and will be expanded as 4.2 approaches its releas
 
    GitHub issue: [#14401](https://github.com/rabbitmq/rabbitmq-server/pull/14401)
 
+ * Schema data store (Khepri) read concurrency optimizations that can lead to low doublt digit percent
+   throughput gains on nodes with larger numbers of cores.
+
+   GitHub issue: [#14530](https://github.com/rabbitmq/rabbitmq-server/pull/14530)
+
+ * Two new `rabbitmq.conf`, settings `log.summarize_process_state` and `log.error_logger_format_depth`, can be used
+   to significantly reduce the amount of queue member (replica) state logged in case of an abnormal termination.
+
+   Limiting logging helps avoid memory allocation spikes.
+
+   GitHub issues: [#14349](https://github.com/rabbitmq/rabbitmq-server/discussions/14349), [#14523](https://github.com/rabbitmq/rabbitmq-server/pull/14523)
+
  * When a configured [authentication or authorization backend](https://www.rabbitmq.com/docs/access-control#backends) comes from a known
    plugin but the plugin is not enabled, the node will now refuse to start.