changelog: add entry for per-callsite rate-limited logging

Add an entry under the Unreleased section documenting per-callsite
rate limiting for error, warn, and info level log messages and the
new rate_limited_log_count metric.

Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>

Author: kalyazin

CHANGELOG.md

@@ -14,6 +14,12 @@ and this project adheres to
   support for Vsock Unix domain socket path overriding on snapshot restore. More
   information can be found in the
   [docs](docs/vsock.md/#unix-domain-socket-renaming).
+- [#5799](https://github.com/firecracker-microvm/firecracker/pull/5799): Add
+  per-callsite rate limiting for error, warn, and info level log messages.
+  Each callsite independently allows up to 10 messages per 5-second window.
+  When logging resumes after suppression, a warn-level summary reports the
+  count of suppressed messages. A new `rate_limited_log_count` metric tracks
+  the total number of suppressed messages.
 
 ### Changed