fix: Ensure invalid spans are ignored for trace propagation

[mydea]

In OTEL, you can have invalid spans being created sometimes (e.g. when a non recording span is created that is not continuing anything). These spans have a 000 span/trace ID. We should consider this as "no span" in our trace propagation code, and use the propagation context one instead, as otherwise we send 000000-0000-0 headers everywhere 😬

I'll need to add at least some tests for this, but want to see how much of an impact this is right now...

[github-actions[bot]]

size-limit report 📦

Path	Size
@sentry/browser	22.22 KB (0%)
@sentry/browser (incl. Tracing)	33.35 KB (+0.14% 🔺)
@sentry/browser (incl. Tracing, Replay)	69.12 KB (+0.06% 🔺)
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	62.46 KB (+0.08% 🔺)
@sentry/browser (incl. Tracing, Replay with Canvas)	73.19 KB (+0.07% 🔺)
@sentry/browser (incl. Tracing, Replay, Feedback)	85.4 KB (+0.07% 🔺)
@sentry/browser (incl. Tracing, Replay, Feedback, metrics)	87.25 KB (+0.06% 🔺)
@sentry/browser (incl. metrics)	26.5 KB (0%)
@sentry/browser (incl. Feedback)	38.45 KB (0%)
@sentry/browser (incl. sendFeedback)	26.85 KB (0%)
@sentry/browser (incl. FeedbackAsync)	31.45 KB (0%)
@sentry/react	24.96 KB (0%)
@sentry/react (incl. Tracing)	36.38 KB (+0.07% 🔺)
@sentry/vue	26.32 KB (0%)
@sentry/vue (incl. Tracing)	35.21 KB (+0.13% 🔺)
@sentry/svelte	22.35 KB (0%)
CDN Bundle	23.41 KB (0%)
CDN Bundle (incl. Tracing)	35.07 KB (+0.08% 🔺)
CDN Bundle (incl. Tracing, Replay)	69.2 KB (+0.05% 🔺)
CDN Bundle (incl. Tracing, Replay, Feedback)	74.4 KB (+0.04% 🔺)
CDN Bundle - uncompressed	68.76 KB (0%)
CDN Bundle (incl. Tracing) - uncompressed	103.76 KB (+0.15% 🔺)
CDN Bundle (incl. Tracing, Replay) - uncompressed	214.23 KB (+0.08% 🔺)
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	226.9 KB (+0.07% 🔺)
@sentry/nextjs (client)	36.27 KB (+0.11% 🔺)
@sentry/sveltekit (client)	33.98 KB (+0.12% 🔺)
@sentry/node	113.02 KB (+0.03% 🔺)
@sentry/node - without tracing	90.43 KB (+0.04% 🔺)
@sentry/aws-serverless	99.51 KB (+0.04% 🔺)