Fix Django span finalization for StreamingHttpResponse

[saisharan0103]

Fixes #4681.

The Django middleware currently starts the server span in process_request with a use_span activation that ends on exit, then exits that activation in process_response. For StreamingHttpResponse, process_response runs before Django consumes the response iterator, and Django only calls response.close() after streaming finishes. That causes the span end time, request duration metrics, and active request decrement to be recorded before the actual response lifecycle is complete.

This changes the middleware so process_response detaches the span context without ending the span there. It wraps response.close so the original close always runs first, then OpenTelemetry finalization runs in a finally block after the response is closed. The existing duration metric recording, active request decrement, and span.end() call now live in a small once-only finalizer used by the close wrapper.

process_response still handles response attributes, propagator injection, hooks, and exception recording.

Regression coverage adds streaming response views and tests for WSGI and ASGI middleware paths. The tests assert that no server span is exported until the streaming response is consumed and closed, then assert the exported span has the expected HTTP attributes.

ruff check instrumentation/opentelemetry-instrumentation-django/src/opentelemetry/instrumentation/django/middleware/otel_middleware.py instrumentation/opentelemetry-instrumentation-django/tests/test_middleware.py instrumentation/opentelemetry-instrumentation-django/tests/test_middleware_asgi.py instrumentation/opentelemetry-instrumentation-django/tests/views.py reports no new findings on the changed files.
Ran pytest -x locally with no new failures.

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