Fix DataClass.parseJson missing import prefix in modular mode

[hhDream]

Problem

When using write_from_json_string_constructor: true with drift_dev:modular mode, the generated fromJsonString constructor contains a bare DataClass.parseJson(...) reference without the import alias prefix (e.g. i0.), causing a compile error.

This is because data_class_writer.dart hard-codes the string DataClass instead of using _emitter.drift('DataClass') like the rest of the file does.

Fix

Use _emitter.drift('DataClass') to generate the correctly prefixed reference. This produces i0.DataClass.parseJson(...) in modular mode and DataClass.parseJson(...) in non-modular mode - both correct.

Reproduction

build.yaml:

drift_dev:modular:
  enabled: true
  options:
    write_from_json_string_constructor: true

Before fix (generated code, will not compile):

factory XxxData.fromJsonString(String encodedJson, ...) =>
    XxxData.fromJson(DataClass.parseJson(encodedJson) as Map<String, dynamic>, ...);
//                   ^^^^^^^^^ unresolved - drift is imported as i0

After fix:

factory XxxData.fromJsonString(String encodedJson, ...) =>
    XxxData.fromJson(i0.DataClass.parseJson(encodedJson) as Map<String, dynamic>, ...);

Closes #3774

[simolus3]

Thanks!