fix(logs): Ensure logs can be flushed correctly

[andreiborza]

resolves #16110

Stores the Client to LogBuffer WeakMap onto the global object so logs can be retrieved correctly during flushing. Previously, the WeakMap reference would be different at flush time, causing no logs to be found for any given client.

Adds an express e2e tests to ensure logs are flushed correctly.

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	23.35 KB	+0.03%	+7 B 🔺
@sentry/browser - with treeshaking flags	23.19 KB	+0.1%	+22 B 🔺
@sentry/browser (incl. Tracing)	37.25 KB	+0.07%	+23 B 🔺
@sentry/browser (incl. Tracing, Replay)	74.47 KB	+0.03%	+19 B 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	68.34 KB	+0.03%	+17 B 🔺
@sentry/browser (incl. Tracing, Replay with Canvas)	79.12 KB	+0.02%	+15 B 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	90.93 KB	-	-
@sentry/browser (incl. Feedback)	39.75 KB	+0.07%	+26 B 🔺
@sentry/browser (incl. sendFeedback)	27.98 KB	+0.07%	+20 B 🔺
@sentry/browser (incl. FeedbackAsync)	32.74 KB	+0.06%	+20 B 🔺
@sentry/react	25.16 KB	+0.11%	+26 B 🔺
@sentry/react (incl. Tracing)	39.24 KB	+0.05%	+17 B 🔺
@sentry/vue	27.63 KB	+0.08%	+22 B 🔺
@sentry/vue (incl. Tracing)	39.01 KB	+0.05%	+18 B 🔺
@sentry/svelte	23.38 KB	+0.07%	+15 B 🔺
CDN Bundle	24.55 KB	+0.01%	+1 B 🔺
CDN Bundle (incl. Tracing)	37.29 KB	-0.03%	-9 B 🔽
CDN Bundle (incl. Tracing, Replay)	72.33 KB	-0.01%	-6 B 🔽
CDN Bundle (incl. Tracing, Replay, Feedback)	77.64 KB	+0.03%	+17 B 🔺
CDN Bundle - uncompressed	71.62 KB	+0.01%	+2 B 🔺
CDN Bundle (incl. Tracing) - uncompressed	110.34 KB	+0.01%	+2 B 🔺
CDN Bundle (incl. Tracing, Replay) - uncompressed	221.63 KB	+0.01%	+2 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	234.15 KB	+0.01%	+2 B 🔺
@sentry/nextjs (client)	40.84 KB	+0.03%	+10 B 🔺
@sentry/sveltekit (client)	37.73 KB	+0.03%	+10 B 🔺
@sentry/node	144.33 KB	+0.02%	+21 B 🔺
@sentry/node - without tracing	96.21 KB	+0.02%	+19 B 🔺
@sentry/aws-serverless	120.57 KB	+0.02%	+13 B 🔺

View base workflow run

[AbhiPrasad]

Thanks for investigating this @andreiborza!

[mydea]

Could this also be the cause of #15793?