chore(nextjs): Move withSentry into withSentryAPI module

[lobsterkatie]

This moves withSentry.ts (and its corresponding test file) to live alongside our other withSentryX wrappers. More specifically, it moves withSentry's types into a new wrappers/types file, and moves its functions into withSentryAPI, since withSentryAPI is becoming the primary wrapper and withSentry is becoming just a helper function.

Note: This is one step in a slightly larger reorganization I want to do in the nextjs SDK, now that it's matured a bit and we have a better idea of what files it needs to contain. For both ease of review and my own time management, I'm going to split the changes up over several PRs and do each as they become relevant and/or start to bug me enough that I fix them.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.47 KB (+0.22% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	60.16 KB (+0.14% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.06 KB (+0.03% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	53.08 KB (+0.13% 🔺)
@sentry/browser - Webpack (gzipped + minified)	19.85 KB (+0.2% 🔺)
@sentry/browser - Webpack (minified)	64.49 KB (+0.18% 🔺)
@sentry/react - Webpack (gzipped + minified)	19.88 KB (+0.2% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	44.73 KB (-0.02% 🔽)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	25.93 KB (+0.2% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.33 KB (+0.07% 🔺)