function decorator for adding code level attributes to span

[wangzlei]

Description of changes:

This PR is preparing code-level span attributes in ADOT Python library instrumentation.

1. Feature control by environment variable "OTEL_AWS_CODE_CORRELATION_ENABLED"
2. A decorator add_code_attributes_to_span support adding the decorated function's code level information into the current span. Refer to https://opentelemetry.io/docs/specs/semconv/code/

file: test.py
line 10  @add_code_attributes_to_span
line 11  def my_function():
               pass

span will have attributes:

{
  "code.function.name": "my_function",
  "code.file.path": "test.py",
  "code.line.number": 11
}

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.