Report dropped spans in client reports

[krystofwoldrich]

Description

Meta issue: https://github.com/getsentry/projects/issues/70

### Blocked by
- [ ] https://github.com/getsentry/sentry-java/issues/3527
- [ ] https://github.com/getsentry/sentry-cocoa/issues/4156
- [ ] https://github.com/getsentry/sentry-javascript/issues/12727

[krystofwoldrich]

Recording dropped spans was implemented in JS v8, so RN will get this in RN SDK v6.

Or the recording will have to be backported to JS SDK v7.

[krystofwoldrich]

Released in https://github.com/getsentry/sentry-react-native/releases/tag/5.30.0