Add changelog entries

Author: kdaily

.changes/next-release/enhancement-awscrt-35781.json

@@ -0,0 +1,5 @@
+{
+  "type": "enhancement",
+  "category": "awscrt",
+  "description": "Update awscrt version requirement to 0.25.7"
+}

.changes/next-release/enhancement-cloudfront-1337.json

@@ -0,0 +1,5 @@
+{
+  "type": "enhancement",
+  "category": "``cloudfront``",
+  "description": "Replace cryptographic functions from ``cryptography`` with ``awscrt`` for the ``sign`` command. Fixes `#9258 <https://github.com/aws/aws-cli/issues/9258>`__."
+}