feat(flags): add utils and flag context need for feature flag integrations

[aliu39]

Notion doc by @cmanallen , summarizing our goal, constraints, and potential approaches: https://www.notion.so/sentry/Feature-Flags-JavaScript-SDK-1358b10e4b5d805288abe1a4fede75ed?pvs=4

This PR implements approach 1. The follow-up is #14195

Split from #14130

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	22.78 KB	+0.1%	+22 B 🔺
@sentry/browser - with treeshaking flags	21.56 KB	+0.1%	+22 B 🔺
@sentry/browser (incl. Tracing)	35.2 KB	+0.08%	+26 B 🔺
@sentry/browser (incl. Tracing, Replay)	71.93 KB	+0.04%	+24 B 🔺
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	62.36 KB	+0.04%	+22 B 🔺
@sentry/browser (incl. Tracing, Replay with Canvas)	76.24 KB	+0.03%	+23 B 🔺
@sentry/browser (incl. Tracing, Replay, Feedback)	89.05 KB	+0.03%	+26 B 🔺
@sentry/browser (incl. Feedback)	39.92 KB	+0.05%	+18 B 🔺
@sentry/browser (incl. sendFeedback)	27.43 KB	+0.09%	+25 B 🔺
@sentry/browser (incl. FeedbackAsync)	32.22 KB	+0.08%	+24 B 🔺
@sentry/react	25.54 KB	+0.1%	+25 B 🔺
@sentry/react (incl. Tracing)	38.17 KB	+0.07%	+24 B 🔺
@sentry/vue	26.92 KB	+0.08%	+22 B 🔺
@sentry/vue (incl. Tracing)	37.1 KB	+0.09%	+31 B 🔺
@sentry/svelte	22.92 KB	+0.1%	+23 B 🔺
CDN Bundle	24.13 KB	+0.11%	+25 B 🔺
CDN Bundle (incl. Tracing)	37.02 KB	+0.07%	+25 B 🔺
CDN Bundle (incl. Tracing, Replay)	71.69 KB	+0.04%	+26 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback)	77.03 KB	+0.04%	+26 B 🔺
CDN Bundle - uncompressed	70.72 KB	+0.09%	+60 B 🔺
CDN Bundle (incl. Tracing) - uncompressed	109.85 KB	+0.06%	+60 B 🔺
CDN Bundle (incl. Tracing, Replay) - uncompressed	222.37 KB	+0.03%	+60 B 🔺
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	235.58 KB	+0.03%	+60 B 🔺
@sentry/nextjs (client)	38.25 KB	+0.06%	+23 B 🔺
@sentry/sveltekit (client)	35.81 KB	+0.09%	+31 B 🔺
@sentry/node	131.55 KB	+0.02%	+23 B 🔺
@sentry/node - without tracing	95.67 KB	+0.03%	+23 B 🔺
@sentry/aws-serverless	105.93 KB	+0.03%	+26 B 🔺

View base workflow run