fix(v7/bundle): Ensure CDN bundles do not overwrite window.Sentry

[mydea]

This was brought up in Slack - turns out we were always overwriting window.Sentry when a CDN bundle was loaded. This means that if a user e.g. loaded an integration via CDN, which is put on window.Sentry, this was overwritten if the loader fetched the base CDN bundle later.

This probably did not come up earlier because we may handle Sentry.Integrations specially, but not sure. This fix should ensure this works as expected!

[lforst]

dumb and simple. love it.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay, Feedback) - Webpack (gzipped)	80.83 KB (added)
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	71.77 KB (added)
@sentry/browser (incl. Tracing, Replay with Canvas) - Webpack (gzipped)	76.02 KB (added)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	65.38 KB (added)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	35.64 KB (added)
@sentry/browser (incl. browserTracingIntegration) - Webpack (gzipped)	35.53 KB (added)
@sentry/browser (incl. Feedback) - Webpack (gzipped)	31.6 KB (added)
@sentry/browser (incl. sendFeedback) - Webpack (gzipped)	31.61 KB (added)
@sentry/browser - Webpack (gzipped)	22.78 KB (added)
@sentry/browser (incl. Tracing, Replay, Feedback) - ES6 CDN Bundle (gzipped)	79.05 KB (added)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	70.38 KB (added)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	36.06 KB (added)
@sentry/browser - ES6 CDN Bundle (gzipped)	25.29 KB (added)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	221.51 KB (added)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	109.1 KB (added)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	75.83 KB (added)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	39.34 KB (added)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	72.27 KB (added)
@sentry/react - Webpack (gzipped)	22.81 KB (added)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	90.03 KB (added)
@sentry/nextjs Client - Webpack (gzipped)	54.15 KB (added)
@sentry-internal/feedback - Webpack (gzipped)	17.34 KB (added)