fix(browser): Stringify span context in linked traces log statement

[s1gr1d]

I came upon this log Sentry Logger [log]: Adding previous_trace [object Object] link to span [object Object] and this PR fixes this by stringifying the context.

One concern I have with that is that the object could be too large (stringifying takes too long) or circular. But this should be very unlikely in this case. However, if someone else shares this concerns we might change the log to either limit the depth or to only log specific entries of the object (might add bundle size).

Closes #18377

[github-actions[bot]]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	24.8 kB	-	-
@sentry/browser - with treeshaking flags	23.31 kB	-	-
@sentry/browser (incl. Tracing)	41.55 kB	+0.03%	+10 B 🔺
@sentry/browser (incl. Tracing, Profiling)	46.14 kB	+0.02%	+9 B 🔺
@sentry/browser (incl. Tracing, Replay)	79.97 kB	+0.02%	+14 B 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	69.69 kB	-	-
@sentry/browser (incl. Tracing, Replay with Canvas)	84.65 kB	+0.02%	+11 B 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	96.89 kB	+0.02%	+11 B 🔺
@sentry/browser (incl. Feedback)	41.48 kB	-	-
@sentry/browser (incl. sendFeedback)	29.49 kB	-	-
@sentry/browser (incl. FeedbackAsync)	34.47 kB	-	-
@sentry/react	26.52 kB	-	-
@sentry/react (incl. Tracing)	43.75 kB	+0.03%	+9 B 🔺
@sentry/vue	29.25 kB	-	-
@sentry/vue (incl. Tracing)	43.35 kB	+0.03%	+11 B 🔺
@sentry/svelte	24.82 kB	-	-
CDN Bundle	27.21 kB	-	-
CDN Bundle (incl. Tracing)	42.21 kB	-	-
CDN Bundle (incl. Tracing, Replay)	78.75 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback)	84.2 kB	-	-
CDN Bundle - uncompressed	79.96 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	125.34 kB	-	-
CDN Bundle (incl. Tracing, Replay) - uncompressed	241.37 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	254.13 kB	-	-
@sentry/nextjs (client)	45.97 kB	+0.03%	+10 B 🔺
@sentry/sveltekit (client)	41.91 kB	+0.03%	+11 B 🔺
@sentry/node-core	51.27 kB	-	-
@sentry/node	159.44 kB	-	-
@sentry/node - without tracing	92.85 kB	-	-
@sentry/aws-serverless	108.14 kB	-	-

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