ref(replay): Improve isBrowser check

[mydea]

Extracted out of #6316, as these are only semi-related. This should allow us to better evaluate bundle size changes due to WINDOW

For now, just changed the logic a bit to use isNodeEnv under the hood. In a next step we should evaluate if we can remove some of these checks.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.54 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	60.42 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.21 KB (+0.03% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	53.76 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	19.94 KB (0%)
@sentry/browser - Webpack (minified)	65.25 KB (0%)
@sentry/react - Webpack (gzipped + minified)	19.96 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	45.96 KB (0%)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.41 KB (0%)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.83 KB (+0.01% 🔺)
@sentry/replay index.js	63.38 KB (+0.03% 🔺)
@sentry/replay - Webpack (gzipped + minified)	63.39 KB (+0.03% 🔺)
@sentry/replay - Webpack (minified)	204.81 KB (+0.01% 🔺)