fix(core): Avoid looking up client for hasTracingEnabled() if possible

[mydea]

This is a bit weird in that we access the current scope & client etc., even if options are passed. Since we also use this method in init() before we have setup stuff, it seems safer to avoid calling this at all if possible.

This is related to #12054, but not really the cause of it.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser	21.67 KB (0%)
@sentry/browser (incl. Tracing)	32.72 KB (-0.01% 🔽)
@sentry/browser (incl. Tracing, Replay)	68.06 KB (+0.01% 🔺)
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	61.46 KB (+0.01% 🔺)
@sentry/browser (incl. Tracing, Replay with Canvas)	72.1 KB (+0.01% 🔺)
@sentry/browser (incl. Tracing, Replay, Feedback)	84.11 KB (+0.01% 🔺)
@sentry/browser (incl. Feedback)	37.6 KB (0%)
@sentry/browser (incl. sendFeedback)	26.23 KB (0%)
@sentry/browser (incl. FeedbackAsync)	30.6 KB (0%)
@sentry/react	24.36 KB (0%)
@sentry/react (incl. Tracing)	35.68 KB (0%)
@sentry/vue	25.5 KB (-0.01% 🔽)
@sentry/vue (incl. Tracing)	34.51 KB (+0.02% 🔺)
@sentry/svelte	21.8 KB (0%)
CDN Bundle	24.21 KB (0%)
CDN Bundle (incl. Tracing)	34.14 KB (+0.03% 🔺)
CDN Bundle (incl. Tracing, Replay)	67.82 KB (+0.01% 🔺)
CDN Bundle (incl. Tracing, Replay, Feedback)	72.78 KB (+0.01% 🔺)
CDN Bundle - uncompressed	71.21 KB (0%)
CDN Bundle (incl. Tracing) - uncompressed	101.27 KB (+0.03% 🔺)
CDN Bundle (incl. Tracing, Replay) - uncompressed	210.89 KB (+0.02% 🔺)
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	223.19 KB (+0.02% 🔺)
@sentry/nextjs (client)	34.92 KB (+0.03% 🔺)
@sentry/sveltekit (client)	33.29 KB (+0.04% 🔺)
@sentry/node	141 KB (+0.01% 🔺)
@sentry/aws-serverless	128.04 KB (+0.01% 🔺)