chore(test): Add tests for skipping of integrations for otel

[mydea]

This adds some tests to an in-progress branch for skipping auto-instrumentation when enabling the otel instrumenter.

As it is kind of hard to test if integrations run with the current setup (because integrations, by design, only run once on the global hub), I added an extra _wasSkipped property to the instrumentations to allow us to test this.

Not 100% sure if this is ideal, but couldn't come up with something better - happy for other ideas as well! It at least works and tests what we actually want to test, I'd say.

(Note the base for this PR is not master but a different, WIP branch)

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.49 KB (-0.06% 🔽)
@sentry/browser - ES5 CDN Bundle (minified)	60.35 KB (-0.04% 🔽)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.12 KB (-0.19% 🔽)
@sentry/browser - ES6 CDN Bundle (minified)	53.67 KB (-0.07% 🔽)
@sentry/browser - Webpack (gzipped + minified)	19.86 KB (-0.17% 🔽)
@sentry/browser - Webpack (minified)	65.12 KB (+0.01% 🔺)
@sentry/react - Webpack (gzipped + minified)	19.88 KB (-0.18% 🔽)
@sentry/nextjs Client - Webpack (gzipped + minified)	45.78 KB (-0.15% 🔽)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.24 KB (-0.14% 🔽)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.62 KB (-0.21% 🔽)