Fix Django example so spans reach stdout in manual and auto instrumentation

[ocelotl]

Note

This PR is a draft and is not intended to be merged on its own.

It is an attempt to translate the review comments from @xrmx and @ocelotl on #4822 into
actual code changes, so that the discussion can be seen as concrete diffs rather than prose.
The intent is for @BrianPetkovsek to incorporate these changes into #4822 (his PR), which
remains the PR that should ultimately land. Please treat this as a suggestion/reference for
#4822 rather than a competing change.

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Description

The Django instrumentation example claims that JSON span data appears in STDOUT, but no exporter was ever configured, so neither documented run mode actually produced output:

• Manual (python manage.py runserver --noreload): manage.py never set up a TracerProvider/exporter, so spans were created but dropped.
• Auto (opentelemetry-instrument python manage.py runserver --noreload): opentelemetry-instrument defaults to the OTLP exporter, so it tried to ship spans to localhost:4317 and printed nothing to the console.

This PR fixes the example for both scenarios:

• Manual: set up a TracerProvider with a SimpleSpanProcessor(ConsoleSpanExporter()) in manage.py so spans print to stdout immediately.
• Auto: document opentelemetry-instrument --traces_exporter console ... (for both runserver and the uWSGI variant), and instruct commenting out the in-code TracerProvider setup and DjangoInstrumentor().instrument() call.

SimpleSpanProcessor is used rather than BatchSpanProcessor so a span is printed the moment a request completes, matching the example's "you should see output similar to this" narration (a batch processor only flushes on a timer / at shutdown).

Relation to #4822

This supersedes #4822, which added the manual manage.py setup but (a) used BatchSpanProcessor (delayed output) and (b) left the auto-instrumentation path on the default OTLP exporter, so opentelemetry-instrument still produced no console output. This PR addresses the maintainer feedback on that PR by making the auto path work via --traces_exporter console in addition to fixing the manual path.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

How Has This Been Tested?

• tox -e ruff (ruff check + format) passes on docs/examples/django/manage.py
• rstcheck docs/examples/django/README.rst passes
• --traces_exporter console resolves to the console entry point registered by opentelemetry-sdk (opentelemetry.sdk.trace.export:ConsoleSpanExporter)

Does This PR Require a Contrib Repo Change?

• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added (n/a — documentation example fix)
• Documentation has been updated