fix(sveltekit): Detect sentry release before creating the Vite plugin

[Lms24]

In a SvelteKit production build, an error was thrown if the sentry-cli wasn't able to detect a release (for instance because the project is not in a git repo). This PR fixes this by detecting a release value before creating the plugin. The detection mechanism is identical to the mechanism in the NextJS SDK, with the exception of the fallback:

• Try to detect a git commit hash. If this fails,
• return a generated UUID

In NextJS, we just fall back to Next's internal build id. SvelteKit doesn't have such an Id, which is why ultimately, we just generate a UUID instead. However, I'd argue we want to first attempt detecting a commit hash as it is less random and the Sentry CLI does it as well.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.97 KB (-0.35% 🔽)
@sentry/browser - ES5 CDN Bundle (minified)	65.48 KB (-0.28% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	19.51 KB (-0.4% 🔽)
@sentry/browser - ES6 CDN Bundle (minified)	57.94 KB (-0.31% 🔽)
@sentry/browser - Webpack (gzipped + minified)	21.11 KB (-0.35% 🔽)
@sentry/browser - Webpack (minified)	68.89 KB (-0.26% 🔽)
@sentry/react - Webpack (gzipped + minified)	21.14 KB (-0.35% 🔽)
@sentry/nextjs Client - Webpack (gzipped + minified)	48.98 KB (-0.15% 🔽)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	28.54 KB (-0.27% 🔽)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	26.77 KB (-0.3% 🔽)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	45.35 KB (+0.01% 🔺)
@sentry/replay - Webpack (gzipped + minified)	39.28 KB (0%)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	64.22 KB (-0.12% 🔽)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	57.19 KB (-0.13% 🔽)