Revert "fix(core): Only generate eventIds in client"

[AbhiPrasad]

Reverts #6247

Fixes #6380

Reverting the PR that moved the event_id generation into the client because this is causing issues if you have async event processors. Although our processing pipeline uses SyncPromise, async code can sneak in there, and this means that our event id's can be undefined.

Since there is a workaround for the initial perf problem we are electing to just revert.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.6 KB (+0.15% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	60.69 KB (+0.17% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.37 KB (+0.09% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	54.26 KB (+0.2% 🔺)
@sentry/browser - Webpack (gzipped + minified)	20.13 KB (+0.07% 🔺)
@sentry/browser - Webpack (minified)	65.83 KB (+0.12% 🔺)
@sentry/react - Webpack (gzipped + minified)	20.16 KB (+0.09% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	45.96 KB (+0.03% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.44 KB (+0.1% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.87 KB (+0.08% 🔺)
@sentry/replay index.js	37.08 KB (0%)
@sentry/replay - Webpack (gzipped + minified)	37.05 KB (0%)
@sentry/replay - Webpack (minified)	124.54 KB (0%)

[grabbou]

Thank you! Also, if you consider dropping that in the future again, I would appreciate some tips on getting this working with ErrorBoundary! I've run across this PR while searching for a root cause behind 0000000..... Thank you!

[krystofwoldrich]

This also affected RN from 4.10.0 to 4.11.0. Looking forward to the next release.