fix(node): Guard process.env.NODE_ENV access in Spotlight integration

[Lms24]

Seems like the spotlight integration code is possibly ending up in places it shouldn't.
While this PR doesn't adress this, it guards accessing process.env.NODE_ENV which we should do anyway.

Maybe addresses #8377 (comment)

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	65.99 KB (+0.19% 🔺)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	59.59 KB (+0.22% 🔺)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	31.12 KB (0%)
@sentry/browser - Webpack (gzipped)	21.38 KB (-0.01% 🔽)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	62.97 KB (+0.41% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	29.62 KB (+0.33% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped)	21.7 KB (+0.46% 🔺)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	198.31 KB (+0.44% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	89.73 KB (+0.47% 🔺)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	64.71 KB (+0.66% 🔺)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	32.29 KB (+0.22% 🔺)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	66.35 KB (+0.16% 🔺)
@sentry/react - Webpack (gzipped)	21.42 KB (0%)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	83.07 KB (+0.14% 🔺)
@sentry/nextjs Client - Webpack (gzipped)	48.21 KB (0%)
@sentry-internal/feedback - Webpack (gzipped)	16.17 KB (-0.13% 🔽)
@sentry/browser (incl. Tracing, Replay, Feedback) - Webpack (gzipped)	74.63 KB (added)
@sentry/browser (incl. Feedback) - Webpack (gzipped)	29.72 KB (added)
@sentry/browser (incl. Tracing, Replay, Feedback) - ES6 CDN Bundle (gzipped)	71.22 KB (added)