test(nextjs): Add NextJS server-side E2E tests.

[onurtemizkan]

Ref: #6292

• Added 2 server-side behaviour tests in the create-next-app test application.

• This set of tests use Playwright as their runner, but they don't use the browser functionality of it. This is for simplicity and also consistency, as expect.poll is not available in jest runners.

• Not sure triggering a server-side error through a user interaction on browser will make a difference for E2E tests, but it's also an option with this setup.

• The event/transaction ids are returned to the test environment as HTTP responses from the server.

• If the team agrees, this approach has a potential to be generalised while writing other server-side tests. Not updating README for now.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.82 KB (-0.01% 🔽)
@sentry/browser - ES5 CDN Bundle (minified)	61.47 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.5 KB (0%)
@sentry/browser - ES6 CDN Bundle (minified)	54.77 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	20.21 KB (0%)
@sentry/browser - Webpack (minified)	66.17 KB (0%)
@sentry/react - Webpack (gzipped + minified)	20.24 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	47.48 KB (0%)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.74 KB (-0.01% 🔽)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	25.03 KB (+0.01% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	43.12 KB (-0.83% 🔽)
@sentry/replay - Webpack (gzipped + minified)	37.83 KB (-1.01% 🔽)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	60.37 KB (-0.6% 🔽)

[lforst]

Nice! I like the the approach of just using the playwright runner 👍