[v8] Replace custom BrowserTracing routing instrumentations

[mydea]

In v7, new BrowserTracing() accepts a custom routingInstrumentation. We use this in a few places.
The replacement browserTracingIntegration() does not accept this anymore (as it is tightly tied to transactions). Instead, this needs to be refactored to a new format using utility methods to start pageload/transaction spans.

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1. ref(ember): Use new browserTracingIntegration() under the hood #10373
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2. feat(angular): Export custom browserTracingIntegration() #10353
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3. feat(react): React Router v4/v5 integration #10430
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4. React Router v3
5. React Router v6
6. feat(nextjs): Add browserTracingIntegration #10397
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7. feat(sveltekit): Add custom browserTracingIntegration() #10450
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8. Vue Router Instrumentation
9. feat(remix): Add custom browserTracingIntegration #10442
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