feat(core): Emit client reports for unsampled root spans on span start

[mydea]

With this PR, the sample_rate,transaction client report is now consistently emitted at the time when the root span is sampled.

Previously, in Node (OTEL) we did not emit this at all, while in browser we emit it at span end time. This is inconsistent and not ideal. Emitting it in OTEL at span end time is difficult because span.end() is a no-op there and you do not get access to it anywhere. So doing it at span start (=sample time) is easier, and also makes more sense as this is also actually the time when the span is dropped.

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	22.74 KB	-	-
@sentry/browser - with treeshaking flags	21.51 KB	-	-
@sentry/browser (incl. Tracing)	35.39 KB	-0.01%	-2 B 🔽
@sentry/browser (incl. Tracing, Replay)	72.09 KB	-0.01%	-4 B 🔽
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	62.62 KB	-0.01%	-5 B 🔽
@sentry/browser (incl. Tracing, Replay with Canvas)	76.36 KB	-0.01%	-1 B 🔽
@sentry/browser (incl. Tracing, Replay, Feedback)	88.38 KB	-0.01%	-2 B 🔽
@sentry/browser (incl. Feedback)	39.07 KB	-	-
@sentry/browser (incl. sendFeedback)	27.42 KB	-	-
@sentry/browser (incl. FeedbackAsync)	32.25 KB	-	-
@sentry/react	25.49 KB	-	-
@sentry/react (incl. Tracing)	38.14 KB	-0.02%	-5 B 🔽
@sentry/vue	27.07 KB	-0.04%	-9 B 🔽
@sentry/vue (incl. Tracing)	37.24 KB	-0.02%	-4 B 🔽
@sentry/svelte	22.86 KB	-	-
CDN Bundle	24.12 KB	-	-
CDN Bundle (incl. Tracing)	35.7 KB	-0.01%	-2 B 🔽
CDN Bundle (incl. Tracing, Replay)	70.25 KB	-0.01%	-3 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback)	75.46 KB	+0.01%	+4 B 🔺
CDN Bundle - uncompressed	70.47 KB	-	-
CDN Bundle (incl. Tracing) - uncompressed	106.03 KB	-0.01%	-7 B 🔽
CDN Bundle (incl. Tracing, Replay) - uncompressed	216.91 KB	-0.01%	-7 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	229.66 KB	-0.01%	-7 B 🔽
@sentry/nextjs (client)	38.27 KB	-0.01%	-3 B 🔽
@sentry/sveltekit (client)	35.9 KB	+0.01%	+2 B 🔺
@sentry/node	161.53 KB	+0.05%	+67 B 🔺
@sentry/node - without tracing	97.28 KB	+0.01%	+2 B 🔺
@sentry/aws-serverless	127.18 KB	+0.05%	+61 B 🔺

View base workflow run