fix(core): Avoid prolonging idle span when starting standalone span

[Lms24]

While working on #16893 I realized that if we reported a web vital standalone span while an idlespan (e.g. pageload) was still running, we'd restart the idle span's child span timeout (i.e. prolong its duration potentially). Is is unintended because by definition the standalone span should not be associated with a potentially ongoing idle span and its tree.

This can happen, for example when users hide the page while the pageload span is still active, causing web vitals to be reported.

[github-actions]

size-limit report 📦

⚠️ Warning: Base artifact is not the latest one, because the latest workflow run is not done yet. This may lead to incorrect results. Try to re-run all tests to get up to date results.

Path	Size	% Change	Change
@sentry/browser	23.88 kB	-	-
@sentry/browser - with treeshaking flags	22.35 kB	-	-
@sentry/browser (incl. Tracing)	39.75 kB	+0.02%	+5 B 🔺
@sentry/browser (incl. Tracing, Replay)	77.88 kB	+0.01%	+6 B 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	67.71 kB	+0.01%	+5 B 🔺
@sentry/browser (incl. Tracing, Replay with Canvas)	82.58 kB	+0.01%	+6 B 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	94.68 kB	+0.01%	+6 B 🔺
@sentry/browser (incl. Feedback)	40.57 kB	-	-
@sentry/browser (incl. sendFeedback)	28.56 kB	-	-
@sentry/browser (incl. FeedbackAsync)	33.46 kB	-	-
@sentry/react	25.61 kB	-	-
@sentry/react (incl. Tracing)	41.71 kB	+0.03%	+10 B 🔺
@sentry/vue	28.31 kB	-	-
@sentry/vue (incl. Tracing)	41.54 kB	+0.02%	+6 B 🔺
@sentry/svelte	23.9 kB	-	-
CDN Bundle	25.16 kB	-	-
CDN Bundle (incl. Tracing)	39.42 kB	+0.03%	+10 B 🔺
CDN Bundle (incl. Tracing, Replay)	75.39 kB	+0.02%	+12 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback)	80.87 kB	+0.01%	+7 B 🔺
CDN Bundle - uncompressed	73.5 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	116.93 kB	+0.04%	+39 B 🔺
CDN Bundle (incl. Tracing, Replay) - uncompressed	231.1 kB	+0.02%	+39 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	243.91 kB	+0.02%	+39 B 🔺
@sentry/nextjs (client)	43.34 kB	+0.02%	+7 B 🔺
@sentry/sveltekit (client)	40.21 kB	+0.03%	+9 B 🔺
@sentry/node	167.57 kB	-	-
@sentry/node - without tracing	100.3 kB	-	-
@sentry/aws-serverless	128.41 kB	+0.01%	+2 B 🔺

View base workflow run