[ package:vm_service ] 4.0.0 release, Sentinels are now thrown, Future<dynamic> returns are now Future<Response>

Change-Id: Ifd1bf62e3bc33bf14359802086c87b2fd19f3ba9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138561
Reviewed-by: Jacob Richman <jacobr@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

Author: bkonyi

pkg/vm_service/CHANGELOG.md

@@ -1,7 +1,14 @@
 # Changelog
 
+## 4.0.0
+- **breaking**: RPCs which can return a `Sentinel` will now throw the `Sentinel`
+  it is received as a response.
+- **breaking**: RPCs which can return multiple values now return
+  `Future<Response>` rather than `Future<dynamic>`.
+- `RPCError` now implements `Exception`.
+
 ## 3.0.0
-**breaking**: RPCs which have an isolateId parameter now return
+- **breaking**: RPCs which have an isolateId parameter now return
   `Future<dynamic>` as a `Sentinel` can be returned if the target isolate no
   longer exists.