package:build_resolvers v2.4.4

• Refactor BuildAssetUriResolver into AnalysisDriverModel and
  AnalysisDriverFilesystem. Add new implementation of
  AnalysisDriverModel.
• Make resolver only throw SyntaxErrorInAssetException on severe syntax errors
• Add BuildAssetUriResolver.useExperimentalResolver for
  --use-experimental-resolver flag. This will be removed.