Explicity set user.ip_address: {{auto}}

[markushi]

We already set {{auto}} #2860 but don't consider the optionssendDefaultPii flag.

Similar to Cocoa: https://github.com/getsentry/sentry-cocoa/blob/72e34fae44b817d8c12490bbc5c1ce7540f86762/Sources/Sentry/SentryClient.m#L781-L786