chore: CHANGELOG updates

Update changeslogs for godot_dart 0.9.0 and godot_dart_builder 0.7.0

Author: fuzzybinary

src/dart/godot_dart/CHANGELOG.md

@@ -3,6 +3,7 @@
 - Add type safe `SignalX` objects supporting automatic registering / deregistering.
 - Fixed an issue with ScriptInstances not detaching themselves from their Dart counterparts on deletion.
 - Attempted to refactor several files to make analysis faster.
+- Fix weak conversion from `StringName` / `GDString` in `Variant.cast`
 
 ## 0.8.0
 

src/dart/godot_dart_build/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - Add the ability to use @GodotProperty on getters.
 - Allow sending RPC messages to specific peers.
+- Fix generation of RPCs in several situations.
 
 ## 0.6.0