Python dataclass and attrs presets render `[object Promise]` instead of the class body

[yashs33244]

PYTHON_DATACLASS_PRESET and PYTHON_ATTRS_PRESET interpolate renderer.defaultSelf() into a template literal without awaiting it, so the generated class body is the literal string [object Promise].

Reproduce

import { PythonGenerator, PYTHON_DATACLASS_PRESET } from '@asyncapi/modelina';

const generator = new PythonGenerator({ presets: [PYTHON_DATACLASS_PRESET] });
const output = await generator.generate({
  $id: 'User', type: 'object', properties: { name: { type: 'string' } }
});
console.log(output[0].result);

Output:

from dataclasses import dataclass

@dataclass
[object Promise]

Same for PYTHON_ATTRS_PRESET.

defaultSelf() is async, so the self hook just needs to await it (the Pydantic preset already does). I'll open a PR.

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