rel: Prepare 2.8.3 release (#1367)

## Which problem is this PR solving?

Prepares the 2.8.3 release.

## Short description of the changes

- Add change log entry
- Add release notes entry

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Refinery Changelog
 
+## 2.8.3 2024-10-08
+
+### Changes 
+
+- fix: Only set incoming user agent if not already present (#1366) | [Mike Goldsmith](https://github.com/MikeGoldsmith)
+- fix: Put a limit on the size of sampler keys (#1364) | [Kent Quirk](https://github.com/kentquirk)
+- feat: Record original user agent for spans and logs (#1358) | [Mike Goldsmith](https://github.com/MikeGoldsmith)
+- feat: Make collector health check timeout configurable (#1371) | [Yingrong Zhao](https://github.com/vinozzZ)
 
 ## 2.8.2 2024-09-13
 

RELEASE_NOTES.md

@@ -2,6 +2,12 @@
 
 While [CHANGELOG.md](./CHANGELOG.md) contains detailed documentation and links to all the source code changes in a given release, this document is intended to be aimed at a more comprehensible version of the contents of the release from the point of view of users of Refinery.
 
+## Version 2.8.3
+
+This is a bug fix release.
+It fixes a bug when building sampler key using a very high cardinality field. The fix is to only take the first 100 unique field values.
+It also adds support for Refinery to record the original sender user agent in event data under the key `meta.refinery.incoming_user_agent` and adds a configurtion option for the health check timeout.
+
 ## Version 2.8.2
 
 This is a bug fix release.