[OTEL] Test processor & setup with demo app

[mydea]

We want to test the ongoing OpenTelemetry integration work with a proper setup.
For this, we will try to run it against opentelemetry-demo, to identify any problems & fix them along the way.

• Setup for paymentservice (manual instrumentation of Node.js app)
• Setup for frontend (manual & auto instrumentation of Next.js app, including Node.js setup)
• Verify converted span data is correct
• Ensure requests to Sentry are ignored/skipped feat(otel): Ignore outgoing Sentry HTTP requests from otel integration #6116

ref #6000