fix(browser): Ensure idle span duration is adjusted when child spans are ignored

[Lms24]

This PR fixes a problem reported in #17451 where ignoring spans in idle root spans (pageload and navigations most prominently) caused the root span duration to be perceived much longer than reasonable. This is only a problem for idle spans in browser, so this PR applies a pragmatic fix to adjust the end time stamp:

We already adjust the time stamp when we end the idle span. So we might as well at this point take any to-be-removed-because-of-ignoreSpans spans out of this calculation. This should work well enough without throwing a bunch of idle-span specific logic into the client or completely changing the point in the event lifecycle where ignoreSpans is applied.

closes #17451

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	24.22 kB	-	-
@sentry/browser - with treeshaking flags	22.74 kB	-	-
@sentry/browser (incl. Tracing)	40.26 kB	+0.08%	+30 B 🔺
@sentry/browser (incl. Tracing, Replay)	78.63 kB	+0.05%	+34 B 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	68.29 kB	+0.04%	+26 B 🔺
@sentry/browser (incl. Tracing, Replay with Canvas)	83.29 kB	+0.04%	+32 B 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	95.52 kB	+0.04%	+32 B 🔺
@sentry/browser (incl. Feedback)	40.94 kB	-	-
@sentry/browser (incl. sendFeedback)	28.88 kB	-	-
@sentry/browser (incl. FeedbackAsync)	33.78 kB	-	-
@sentry/react	25.93 kB	-	-
@sentry/react (incl. Tracing)	42.26 kB	+0.07%	+29 B 🔺
@sentry/vue	28.71 kB	-	-
@sentry/vue (incl. Tracing)	42.07 kB	+0.07%	+28 B 🔺
@sentry/svelte	24.24 kB	-	-
CDN Bundle	25.75 kB	-	-
CDN Bundle (incl. Tracing)	40.07 kB	+0.05%	+19 B 🔺
CDN Bundle (incl. Tracing, Replay)	76.3 kB	+0.03%	+20 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback)	81.8 kB	+0.02%	+16 B 🔺
CDN Bundle - uncompressed	75.23 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	118.65 kB	+0.06%	+68 B 🔺
CDN Bundle (incl. Tracing, Replay) - uncompressed	233.78 kB	+0.03%	+68 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	246.54 kB	+0.03%	+68 B 🔺
@sentry/nextjs (client)	44.26 kB	+0.08%	+32 B 🔺
@sentry/sveltekit (client)	40.69 kB	+0.07%	+28 B 🔺
@sentry/node-core	49.96 kB	-0.01%	-1 B 🔽
@sentry/node	151.25 kB	-	-
@sentry/node - without tracing	91.87 kB	-	-
@sentry/aws-serverless	105.31 kB	-	-

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[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	9,071	-	8,870	+2%
GET With Sentry	1,398	15%	1,378	+1%
GET With Sentry (error only)	6,169	68%	5,946	+4%
POST Baseline	1,210	-	1,176	+3%
POST With Sentry	541	45%	492	+10%
POST With Sentry (error only)	1,082	89%	988	+10%
MYSQL Baseline	3,372	-	3,255	+4%
MYSQL With Sentry	498	15%	450	+11%
MYSQL With Sentry (error only)	2,736	81%	2,620	+4%

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[mydea]

nice, I like the pragmatic solution ❤️ 👍