[Docs] Backporting 8.16.3 Release Notes to 8.16 (elastic#206878)

## Summary

Adding elastic#206156 to 8.16.

docs/CHANGELOG.asciidoc

@@ -10,6 +10,7 @@
 
 Review important information about the {kib} 8.x releases.
 
+* <<release-notes-8.16.3>>
 * <<release-notes-8.16.2>>
 * <<release-notes-8.16.1>>
 * <<release-notes-8.16.0>>
@@ -82,6 +83,29 @@ Review important information about the {kib} 8.x releases.
 
 include::upgrade-notes.asciidoc[]
 
+[[release-notes-8.16.3]]
+== {kib} 8.16.3
+The 8.16.3 release includes the following bug fixes.
+[float]
+[[fixes-v8.16.3]]
+=== Bug fixes
+Alerting::
+* Updates handling of invalid RRule params and prevents infinite looping ({kibana-pull}205650[#205650]).
+* Fixes an issue with saving ECS group by fields at the root level for query DSL rules ({kibana-pull}203769[#203769]).
+* Fixes race condition in alerting rules data view selector ({kibana-pull}203654[#203654]).
+Data ingestion and Fleet::
+* Fixes an issue with showing all agent tags when agent list is filtered ({kibana-pull}205163[#205163]).
+Elastic Observability solution::
+* Preserves `kuery` filters when switching between Universal Profiling pages in new solution navigation ({kibana-pull}203545[#203545]).
+Elastic Search solution::
+* Adds ML as required plugin to Search Assistant ({kibana-pull}204009[#204009]).
+* Fixes web crawler name inconsistencies ({kibana-pull}202738[#202738]).
+Elastic Security solution::
+For the Elastic Security 8.16.3 release information, refer to {security-guide}/release-notes.html[_Elastic Security Solution Release Notes_].
+Kibana security::
+* Fixes Integration and Datastream name validation ({kibana-pull}204943[#204943]).
+* Adds RBAC to the Automatic Import APIs ({kibana-pull}203882[#203882]).
+
 [[release-notes-8.16.2]]
 == {kib} 8.16.2