WSGI request spans don't have both `http.target` and `http.url` attributes

Steps to reproduce

Example code:

from flask import Flask
from opentelemetry.instrumentation.flask import FlaskInstrumentor
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import ConsoleSpanExporter, SimpleSpanProcessor
from opentelemetry.semconv.trace import SpanAttributes

tracer_provider = TracerProvider()
processor = SimpleSpanProcessor(
    ConsoleSpanExporter(
        formatter=lambda span: str(
            (
                span.attributes.get(SpanAttributes.HTTP_TARGET),
                span.attributes.get(SpanAttributes.HTTP_URL),
            )
        )
    )
)
tracer_provider.add_span_processor(processor)

app = Flask(__name__)
FlaskInstrumentor().instrument_app(app, tracer_provider=tracer_provider)


@app.route('/hello')
def hello():
    return 'hello'


app.run()

Then visit http://localhost:5000/hello

What is the expected behavior?

('/hello', 'http://localhost:5000/hello')

What is the actual behavior?

('/hello', None)

Additional context

The current code looks like this:

https://github.com/open-telemetry/opentelemetry-python-contrib/blob/47caeab7aff47070c565cd90536a39ec5eb06f34/instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py#L320-L325

The first commit of the file shows essentially the same:

https://github.com/open-telemetry/opentelemetry-python-contrib/blob/d19b464a0a23a4a66d5df635634e7d6315cb54db/instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/__init__.py#L108-L111

I don't know under what circumstances the target is missing and the full URL is present instead, but I don't understand why only one or the other is included instead of both.

By comparison, the ASGI instrumentation happily includes both:

https://github.com/open-telemetry/opentelemetry-python-contrib/blob/47caeab7aff47070c565cd90536a39ec5eb06f34/instrumentation/opentelemetry-instrumentation-asgi/src/opentelemetry/instrumentation/asgi/__init__.py#L311-L312

Read instrumentation/opentelemetry-instrumentation-wsgi/src/opentelemetry/instrumentation/wsgi/init.py at the linked lines, then compare the corresponding ASGI instrumentation. Run the Flask reproduction to inspect both attributes; done means the WSGI span reports http.target as /hello and http.url as the full URL.