Add OpenTelemetryIntegration to DEFAULT_INTEGRATIONS

[sentrivana]

Previously, it was only added if the experimental otel_powered_performance flag was on.

We need the integration to be active to set up basic things like the tracer.

[codecov]

❌ 3969 Tests Failed:

Tests completed	Failed	Passed	Skipped
16683	3969	12714	1916

View the top 3 failed tests by shortest run time

tests.integrations.celery.test_celery test_abstract_task[<lambda>2]

Stack Traces | 0s run time

No failure message available

tests.integrations.celery.test_celery test_producer_span_data[redis]

Stack Traces | 0s run time

No failure message available

tests.integrations.celery.test_celery test_simple_without_performance[<lambda>2]

Stack Traces | 0s run time

No failure message available

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