Merge v1.16 LTS changelog to master (#4975)

**Which issue(s) this PR fixes**: 
Fixes #

**What this PR does / why we need it**: 
Merge v1.16 LTS changelog to master
Ref. https://github.com/fluent/fluentd/blob/v1.16/CHANGELOG.md

**Docs Changes**:

**Release Note**:

Signed-off-by: Shizuo Fujita <[email protected]>

Author: Watson1978

CHANGELOG.md

@@ -142,6 +142,50 @@
 
 # v1.16
 
+## Release v1.16.9 - 2025/05/14
+
+### Bug Fix
+
+* winsvc: Fix bug where service accidentally stops after starting.
+  The previous version (v1.16.8) should not be used for Windows Service.
+  https://github.com/fluent/fluentd/pull/4955
+
+### Misc
+
+* CI improvemnts
+  https://github.com/fluent/fluentd/pull/4956
+
+## Release v1.16.8 - 2025/05/01
+
+**This version has a critical bug about Windows Service. Do not use this version.**
+(https://github.com/fluent/fluentd/pull/4955)
+
+### Bug Fix
+
+* winsvc: Stop the service when the supervisor is dead
+  https://github.com/fluent/fluentd/pull/4942
+* formatter_csv: Fix memory leak
+  https://github.com/fluent/fluentd/pull/4920
+
+### Misc
+
+* Add fiddle as dependency gem for Ruby 3.5 on Windows
+  https://github.com/fluent/fluentd/pull/4919
+* Refactoring code
+  https://github.com/fluent/fluentd/pull/4921
+  https://github.com/fluent/fluentd/pull/4922
+  https://github.com/fluent/fluentd/pull/4926
+  https://github.com/fluent/fluentd/pull/4943
+* CI improvemnts
+  https://github.com/fluent/fluentd/pull/4821
+  https://github.com/fluent/fluentd/pull/4850
+  https://github.com/fluent/fluentd/pull/4851
+  https://github.com/fluent/fluentd/pull/4862
+  https://github.com/fluent/fluentd/pull/4915
+  https://github.com/fluent/fluentd/pull/4923
+  https://github.com/fluent/fluentd/pull/4925
+  https://github.com/fluent/fluentd/pull/4927
+
 ## Release v1.16.7 - 2025/01/29
 
 ### Bug Fix