ref(core): Restructure hub exports

[mydea]

To make it a bit easier to replace/refactor them in coming steps.

[mydea]

I also align hub & scope type & class here a bit - more to cleanup here in the future, but step by step...

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay, Feedback) - Webpack (gzipped)	77.8 KB (+0.01% 🔺)
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	69.04 KB (-0.01% 🔽)
@sentry/browser (incl. Tracing, Replay with Canvas) - Webpack (gzipped)	72.97 KB (-0.01% 🔽)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	62.66 KB (-0.01% 🔽)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	33.23 KB (-0.02% 🔽)
@sentry/browser (incl. browserTracingIntegration) - Webpack (gzipped)	33.13 KB (-0.03% 🔽)
@sentry/browser (incl. Feedback) - Webpack (gzipped)	31.15 KB (-0.04% 🔽)
@sentry/browser (incl. sendFeedback) - Webpack (gzipped)	31.15 KB (-0.06% 🔽)
@sentry/browser - Webpack (gzipped)	22.4 KB (-0.17% 🔽)
@sentry/browser (incl. Tracing, Replay, Feedback) - ES6 CDN Bundle (gzipped)	76.08 KB (-0.03% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	67.62 KB (-0.01% 🔽)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	33.57 KB (-0.09% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped)	24.69 KB (-0.07% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	212.81 KB (-0.04% 🔽)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	101.43 KB (-0.08% 🔽)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	73.95 KB (-0.11% 🔽)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	36.82 KB (-0.14% 🔽)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	69.42 KB (+0.01% 🔺)
@sentry/react - Webpack (gzipped)	22.44 KB (-0.11% 🔽)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	87.08 KB (-0.01% 🔽)
@sentry/nextjs Client - Webpack (gzipped)	50.34 KB (-0.05% 🔽)
@sentry-internal/feedback - Webpack (gzipped)	17.1 KB (-0.08% 🔽)