feat(nextjs): Don't init SDK on Vercel Edge Runtime

[lforst]

This PR fixes a problem where we crash out of the box on Vercel and also in production builds when the experimental-edge runtime is used in API routes.

We use the fact that Next.js string replaces the global EdgeRuntime when a server bundle is supposed to be run on the edge runtime. If this is the case we no-op Sentry.init and log a message. We also have to not wrap the API routes automatically in that case.

Tried to add quick tests that test if the API routes still crash. But with our integration test setup it was a pita to get working because this is only really a thing for Next.js 12+.

Ref: #6346

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.6 KB (-0.01% 🔽)
@sentry/browser - ES5 CDN Bundle (minified)	60.69 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.37 KB (+0.01% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	54.26 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	20.13 KB (0%)
@sentry/browser - Webpack (minified)	65.83 KB (0%)
@sentry/react - Webpack (gzipped + minified)	20.16 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	47.01 KB (+0.11% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.44 KB (+0.01% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.87 KB (+0.02% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	41.74 KB (0%)
@sentry/replay - Webpack (gzipped + minified)	37.23 KB (0%)

[AbhiPrasad]

LGTM