chore(deps): bump built_value_generator

Bumps the built_value_generator group in /packages/smithy/smithy_codegen with 1 update: [built_value_generator](https://github.com/google/built_value.dart).


Updates `built_value_generator` from 8.10.1 to 8.12.0
- [Release notes](https://github.com/google/built_value.dart/releases)
- [Changelog](https://github.com/google/built_value.dart/blob/master/CHANGELOG.md)
- [Commits](https://github.com/google/built_value.dart/commits)

---
updated-dependencies:
- dependency-name: built_value_generator
  dependency-version: 8.12.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: built_value_generator
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

packages/smithy/smithy_codegen/pubspec.yaml

@@ -13,11 +13,11 @@ dependencies:
   aws_signature_v4: any
   build_cli_annotations: ^2.0.0
   built_collection: ^5.1.1
-  built_value: ^8.10.1
+  built_value: ^8.12.0
   code_builder: ^4.10.1
   collection: ^1.18.0
   crclib: ^3.0.0
-  dart_style: ^3.0.1
+  dart_style: ^3.1.2
   fixnum: ^1.0.0
   grpc: ^4.0.0
   html2md: ^1.2.5
@@ -38,12 +38,12 @@ dependencies:
 
 dev_dependencies:
   amplify_lints: ">=3.1.0 <3.2.0"
-  build_cli: ^2.1.6
-  build_runner: ^2.4.9
+  build_cli: ^2.2.8
+  build_runner: ^2.8.0
   build_verify: ^3.0.0
-  build_version: ^2.1.1
-  built_value_generator: ^8.10.1
-  json_serializable: ">=6.9.4 <6.10.0"
+  build_version: ^2.1.3
+  built_value_generator: ^8.12.0
+  json_serializable: ^6.11.1
   smithy_test:
     path: ../smithy_test
   test: ^1.22.1