Implement sendDefaultPii behaviour in the JS SDKs

[Lms24]

Extracted from #5340

This issue tracks the second step of adding the sendDefaultPii SDK init option to the JS SDK. Currently, the flag is only used to avoid sensitive data being propagated in distributed tracing via the dynamic sampling context. In v8, we'll add the additional behaviour of this flag as described in the Sentry SDK development specification

[HazAT]

Linking getsentry/rfcs#62

[HazAT]

Related: #4777

[HazAT]

Related: #6389

[mydea]

So some notes for this:

1. In browser, we want to guard adding the {{auto}} value in all the places introduced here: feat(browser): Set user.ip_address explicitly to {{auto}} #15008 to only be set when sendDefaultPii: true is configured.
2. In node, we need to decide - currently, the ip address is opt-in by passing requestDataIntegration({ ip: true }). We may want to instead guard this based on sendDefaultPii too. Possibly, the logic can be: const sendIpAddress = options.ip || clientOptions.sendDefaultPii 🤔

[Lms24]

options.ip || clientOptions.sendDefaultPii

shouldn't this rather be options.ip ?? clientOptions.sendDefaultPii? Otherwise there's no way to opt out of IP collection granularly, right?