support code attributes for django

[wangzlei]

Description of changes:
If set environment variable OTEL_AWS_CODE_CORRELATION_ENABLED=true, django server spans have code-level information.

        "http.route": "template/",
        "code.function.name": "views.TestTemplateView.get",
        "code.file.path": "/Volumes/workplace/extension/aws-otel-python-instrumentation/samples/django/views.py",
        "code.line.number": 59,
        "http.status_code": 200

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