fix(browser): Make sure measure spans have valid start timestamps

[AbhiPrasad]

resolves #12281

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser	22.22 KB (0%)
@sentry/browser (incl. Tracing)	33.38 KB (+0.21% 🔺)
@sentry/browser (incl. Tracing, Replay)	69.16 KB (+0.11% 🔺)
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	62.49 KB (+0.12% 🔺)
@sentry/browser (incl. Tracing, Replay with Canvas)	73.22 KB (+0.11% 🔺)
@sentry/browser (incl. Tracing, Replay, Feedback)	85.82 KB (+0.09% 🔺)
@sentry/browser (incl. Tracing, Replay, Feedback, metrics)	87.68 KB (+0.09% 🔺)
@sentry/browser (incl. metrics)	26.5 KB (0%)
@sentry/browser (incl. Feedback)	38.86 KB (0%)
@sentry/browser (incl. sendFeedback)	26.84 KB (0%)
@sentry/browser (incl. FeedbackAsync)	31.45 KB (0%)
@sentry/react	24.97 KB (0%)
@sentry/react (incl. Tracing)	36.43 KB (+0.18% 🔺)
@sentry/vue	26.33 KB (0%)
@sentry/vue (incl. Tracing)	35.24 KB (+0.2% 🔺)
@sentry/svelte	22.36 KB (0%)
CDN Bundle	23.42 KB (0%)
CDN Bundle (incl. Tracing)	35.12 KB (+0.21% 🔺)
CDN Bundle (incl. Tracing, Replay)	69.25 KB (+0.11% 🔺)
CDN Bundle (incl. Tracing, Replay, Feedback)	74.45 KB (+0.1% 🔺)
CDN Bundle - uncompressed	68.8 KB (0%)
CDN Bundle (incl. Tracing) - uncompressed	103.82 KB (+0.16% 🔺)
CDN Bundle (incl. Tracing, Replay) - uncompressed	214.29 KB (+0.08% 🔺)
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	227 KB (+0.08% 🔺)
@sentry/nextjs (client)	36.3 KB (+0.19% 🔺)
@sentry/sveltekit (client)	34.02 KB (+0.2% 🔺)
@sentry/node	130.61 KB (-0.01% 🔽)
@sentry/node - without tracing	91.63 KB (0%)
@sentry/aws-serverless	116.8 KB (0%)