feat: Export browser integrations individually

[AbhiPrasad]

Currently users consume integrations like so:

const INTEGRATIONS = {
  ...windowIntegrations,
  ...CoreIntegrations,
  ...BrowserIntegrations,
};

export { INTEGRATIONS as Integrations };

This cannot be tree-shaken because a new object is being constructed with multiple object spreads.

In this PR, we switch to exporting everything individually. This means users don't have import the entire INTEGRATIONS object in, allowing it to be treeshaken.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	18.74 KB (-6.96% 🔽)
@sentry/browser - ES5 CDN Bundle (minified)	58.55 KB (-9.38% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	17.55 KB (-6.95% 🔽)
@sentry/browser - ES6 CDN Bundle (minified)	52.73 KB (-9.03% 🔽)
@sentry/browser - Webpack (gzipped + minified)	19.21 KB (-17.35% 🔽)
@sentry/browser - Webpack (minified)	62.08 KB (-24.03% 🔽)
@sentry/react - Webpack (gzipped + minified)	19.23 KB (-17.39% 🔽)
@sentry/nextjs Client - Webpack (gzipped + minified)	42.9 KB (-10.73% 🔽)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	24.51 KB (-5.99% 🔽)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	23.09 KB (-5.67% 🔽)

[lforst]

🎄