feat(core): emit beforeEnvelope hook

[JonasBa]

Emit beforeEnvelope event on the client when sending event.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	20.41 KB (+0.07% 🔺)
@sentry/browser - ES5 CDN Bundle (minified)	63.3 KB (+0.05% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.99 KB (+0.06% 🔺)
@sentry/browser - ES6 CDN Bundle (minified)	56.21 KB (+0.06% 🔺)
@sentry/browser - Webpack (gzipped + minified)	20.65 KB (+0.07% 🔺)
@sentry/browser - Webpack (minified)	67.44 KB (+0.05% 🔺)
@sentry/react - Webpack (gzipped + minified)	20.68 KB (+0.07% 🔺)
@sentry/nextjs Client - Webpack (gzipped + minified)	52.09 KB (+7.29% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	33.66 KB (+21.78% 🔺)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	26 KB (+0.38% 🔺)
@sentry/replay ES6 CDN Bundle (gzipped + minified)	43.17 KB (0%)
@sentry/replay - Webpack (gzipped + minified)	37.19 KB (0%)
@sentry/browser + @sentry/tracing + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	61.3 KB (+0.18% 🔺)
@sentry/browser + @sentry/replay - ES6 CDN Bundle (gzipped + minified)	54.39 KB (+0.03% 🔺)

[AbhiPrasad]

shouldn't this be called above forEachEnvelopeItem?

[JonasBa]

Ah right, idk why I placed it here but yes, it def should be. Do I even need to feature check here btw, can I just client.emit...?

[mydea]

emit may be unavailable when using a custom client, so until v8 we need to guard this, sadly!

[JonasBa]

@AbhiPrasad @mydea
There seems to be a problem that is unrelated to my changes - I keep seeing this error in e2e tests

  > @sentry-internal/tracing:"build:tarball"
  
  $ ts-node ../../scripts/prepack.ts --bundles && npm pack ./build/npm
  
  ERROR: Directory 'build/npm' does not exist in @sentry-internal/tracing.
  This script should only be executed after you've run `yarn build`.

[AbhiPrasad]

Tests are too flaky 😭

[JonasBa]

hehe yeah, I have been restarting them 😅