Various fixes & improvements
- Restore original behavior by always creating a span (#3005) by @antonpirker
- Merge baggage headers (incoming and new created ones) (#3001) by @antonpirker
- Fix duplicate baggage headers in Celery integration introduced in SDK 2.0 (#2993) by @antonpirker
- Make it work with old and new newrelic versions (#2999) by @antonpirker
- docs: Update migration guide wording (#2987) by @colin-sentry
- docs: Tweak migration guide (#2979) by @colin-sentry
- Small updates to migration guide (#2911) by @colin-sentry
- Update CHANGELOG.md (51a906c) by @sentrivana
- release: 1.45.0 (7570e39) by @getsentry-bot