fix(opentelemetry): Ensure DSC propagation works correctly

[mydea]

This updates the propagation handling in OTEL to the following:

1. If there is an active (local) span, we always pick up propagation context/DSC data from it.
2. Else, we try to pick it from the current scope
3. If we can't find this (e.g. a detached otel context is used), we try to pick it from the remote span context
4. Finally, if that also fails, we have no DSC

Closes #10899

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay, Feedback) - Webpack (gzipped)	77.21 KB (-0.25% 🔽)
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	68.46 KB (-0.22% 🔽)
@sentry/browser (incl. Tracing, Replay with Canvas) - Webpack (gzipped)	72.4 KB (-0.21% 🔽)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	62.01 KB (-0.26% 🔽)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	32.67 KB (-0.53% 🔽)
@sentry/browser (incl. browserTracingIntegration) - Webpack (gzipped)	32.67 KB (-0.53% 🔽)
@sentry/browser (incl. Feedback) - Webpack (gzipped)	31.02 KB (-0.15% 🔽)
@sentry/browser (incl. sendFeedback) - Webpack (gzipped)	31.02 KB (-0.13% 🔽)
@sentry/browser - Webpack (gzipped)	22.27 KB (-0.12% 🔽)
@sentry/browser (incl. Tracing, Replay, Feedback) - ES6 CDN Bundle (gzipped)	75.37 KB (-0.61% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	67.03 KB (-0.63% 🔽)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	32.87 KB (-1.26% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped)	24.55 KB (-0.97% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	210.31 KB (-0.37% 🔽)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	99.04 KB (-0.77% 🔽)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	73.45 KB (-0.84% 🔽)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	35.95 KB (-1.12% 🔽)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	68.74 KB (-0.2% 🔽)
@sentry/react - Webpack (gzipped)	22.3 KB (-0.11% 🔽)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	85.19 KB (-0.21% 🔽)
@sentry/nextjs Client - Webpack (gzipped)	49.53 KB (-0.33% 🔽)
@sentry-internal/feedback - Webpack (gzipped)	17.09 KB (0%)

[lforst]

Lgtm!