fix(sveltekit): Don't crash build when CLI credentials are missing

[Lms24]

Previously, a project build would crash when users didn't specify org, project slugs or auth tokens. This PR fixes that by catching the error and providing additional information to the Sentry CLI error message.

ref #7669

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.98 KB (+0.02% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	65.55 KB (-0.03% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	19.53 KB (+0.03% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	57.99 KB (-0.02% 🔽)
@sentry/browser - Webpack (gzipped + minified)	21.13 KB (-0.03% 🔽)
@sentry/browser - Webpack (minified)	68.95 KB (-0.02% 🔽)
@sentry/react - Webpack (gzipped + minified)	21.15 KB (-0.03% 🔽)
@sentry/nextjs Client - Webpack (gzipped + minified)	49 KB (+0.12% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	28.55 KB (+0.04% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	26.78 KB (+0.06% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	44.92 KB (-0.01% 🔽)
@sentry/replay - Webpack (gzipped + minified)	38.88 KB (+0.06% 🔺)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	63.84 KB (+0.04% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	56.87 KB (+0.02% 🔺)