Introduce a substitute value for AnnotatedValue.removed_because_over_size_limit and AnnotatedValue.removed_because_raw_data

[ericapisani]

We generally try to avoid setting none or empty strings on span attributes because it doesn't provide any meaningful information to users and increases the size of the envelope.

In scenarios where, within an integration, we are setting the request body data on a span attribute, and that request data is removed/annotated for some reason, we should set a value to indicate the reason why that data was removed.

[linear-code]

PY-2396