extract serializers to seperate package (#457)

* extract serializers to seperate package

* clean pubspec

* compat with new dio version, return uint8list in test mocks instead of list<int>

Author: knaeckeKami

codegen/end_to_end_test/lib/fragments/__generated__/hero_with_interface_subtyped_fragments.data.gql.dart

@@ -9,9 +9,10 @@ dependencies:
   built_collection: ^5.0.0
   built_value: ^8.0.6
   gql_exec: ^1.0.0
-  gql_build: ^0.8.0
-  gql_code_builder: ^0.7.1
+  gql_code_builder_serializers: ^0.1.0
 dev_dependencies: 
   build: ^2.0.0
   build_runner: ^2.0.0
   test: ^1.16.8
+  gql_code_builder: ^0.7.1
+  gql_build: ^0.8.0

codegen/end_to_end_test/lib/graphql/__generated__/schema.schema.gql.dart

@@ -9,10 +9,11 @@ dependencies:
   built_collection: ^5.0.0
   built_value: ^8.0.6
   gql_exec: ^1.0.0
-  gql_build: ^0.8.0
-  gql_code_builder: ^0.7.1
+  gql_code_builder_serializers: ^0.1.0
 dev_dependencies: 
   build: ^2.0.0
   build_runner: ^2.0.0
   test: ^1.16.8
   gql_tristate_value: ^1.0.0
+  gql_build: ^0.8.0
+  gql_code_builder: ^0.7.1