feat(sveltekit): Convert sentryHandle to a factory function

[Lms24]

This PR converts the sentyHandle server-side request handler to a factory function instead of a plain handler. This will allow us more freedom down the line to permit customization by passing options to the handler.
More details in #7951

Unfortunately, this is a breaking change but we need to change this now while the SDK is not yet stable.

closes #7951

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	21.03 KB (+0.01% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	65.66 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	19.56 KB (+0.01% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	58.12 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	21.17 KB (0%)
@sentry/browser - Webpack (minified)	69.07 KB (0%)
@sentry/react - Webpack (gzipped + minified)	21.19 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	49.03 KB (0%)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	28.59 KB (0%)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	26.82 KB (+0.01% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	46.81 KB (+0.54% 🔺)
@sentry/replay - Webpack (gzipped + minified)	40.59 KB (+0.57% 🔺)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	65.62 KB (+0.43% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	58.57 KB (+0.42% 🔺)