Documents and Use sendDefaultPii=true in docs and in product getting started guide

[krystofwoldrich]

Description

• Umbrella issue Document and add sendDefaultPii: true to onboarding docs team-sdks#121 and Document data collected by SDKs team-sdks#82

### Waiting for (needs to be done first)
- [ ] Java/Android Pii docs https://github.com/getsentry/sentry-java/issues/4092
- [ ] Cocoa Pii docs https://github.com/getsentry/sentry-docs/issues/12751
- [ ] JavaScript docs https://github.com/getsentry/sentry-java/issues/4092

- [ ] Add to RN docs (link native docs and javascript, note RN specifics)
- [ ] Add to RN in product getting started
- [ ] Add to sentry/wizard code snippet