Update changelogs to prepare for crate release (#1470)

Updates the changelogs so that crates can be updated prior to the
release of MP v1.19.0

### Does this change impact existing behavior?

Does not impact behaviour.

### Does this change need a changelog entry? Does it require a version
change?

No, the crate update itself does not need a changelog entries. Version
changes were already done in #1468

---

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license and I agree to the terms of
the [Developer Certificate of Origin
(DCO)](https://developercertificate.org/).

Signed-off-by: Christian Hagemeier <chagem@amazon.com>

Author: c-hagem

mountpoint-s3-client/CHANGELOG.md

@@ -1,4 +1,6 @@
-## Unreleased (v0.16.0)
+## Unreleased
+
+## v0.16.0 (Jun 19, 2025)
 
 * Add support for RenameObject API. ([#1468](https://github.com/awslabs/mountpoint-s3/pull/1468))
 

mountpoint-s3-fs/CHANGELOG.md

@@ -1,4 +1,6 @@
-## Unreleased (v0.5.0)
+## Unreleased
+
+## v0.5.0 (Jun 19, 2025)
 
 * Add support for renaming files on buckets supporting the RenameObject API. ([#1468](https://github.com/awslabs/mountpoint-s3/pull/1468))
 

mountpoint-s3/CHANGELOG.md

@@ -1,4 +1,6 @@
-## Unreleased (v1.19.0)
+## Unreleased
+
+## v1.19.0 (Jun 19, 2025)
 
 * Add support for renaming files using the RenameObject API when mounting directory buckets in S3 Express One Zone. ([#1468](https://github.com/awslabs/mountpoint-s3/pull/1468))