Explicity set `user.ip_address: {{auto}}`

[cleptric]

Description

For client side SDKs, we need to explicitly set the user's IP address to {{auto}}, if the property was not set by the user.

By default, SDKs should not set {{auto}} and only do so if sendDefaultPii was set to true by the user.

Docs: https://develop.sentry.dev/sdk/expected-features/data-handling/

See getsentry/relay#4431

Stakeholder(s)

@jjbayer

Team(s)

Mobile, Web Frontend, GDX

SDKs

## SDKs
- [x] Flutter: https://github.com/getsentry/sentry-dart/pull/2726
- [x] Dart SDK - Depends on Flutter SDK
- [x] Apple/Cocoa SDK https://github.com/getsentry/sentry-cocoa/blob/72e34fae44b817d8c12490bbc5c1ce7540f86762/Sources/Sentry/SentryClient.m#L781-L786
- [ ] https://github.com/getsentry/sentry-java/issues/4068
- [x] Kotlin Multiplatform SDK - depends on Apple/Cocoa and Java/Android SDK
- [x] Electron SDK - https://github.com/getsentry/sentry-electron/pull/1057
- [x] JavaScript SDK - https://github.com/getsentry/sentry-javascript/pull/15008 & https://github.com/getsentry/sentry-javascript/issues/5347
- [x] .NET SDK - https://github.com/getsentry/sentry-dotnet/pull/3893
- [x] Unity SDK - Inherits it from the .NET SDK, see above.
- [x] PowerShell SDK - Inherits it from the .NET SDK, see above.
- [ ] Capacitor SDK https://github.com/getsentry/sentry-capacitor/issues/819
- [ ] Cordova SDK https://github.com/getsentry/sentry-cordova/issues/369
- [ ] React Native SDK https://github.com/getsentry/sentry-react-native/issues/4462
- [ ] Unreal SDK

[bruno-garcia]

@bitsandfoxes I'm pretty sure Unity does the right thing (the dotnet sdk that is, which would be true then for Unity, Xamarin and PowerShell. But could you please double check?

[kahest]

sentry-cocoa already sets {{auto}} in https://github.com/getsentry/sentry-cocoa/blob/72e34fae44b817d8c12490bbc5c1ce7540f86762/Sources/Sentry/SentryClient.m#L781-L786, marking as done

[jjbayer]

for spans, relay populates the client.address attribute (even if no explicit auto is set):
https://github.com/getsentry/relay/blob/2e5e53191f4cf960b49bed86ab6564552084a0b1/relay-server/src/services/processor/span/processing.rs#L582-L590

for sessions there's the ip_address attribute:
https://github.com/getsentry/relay/blob/2e5e53191f4cf960b49bed86ab6564552084a0b1/relay-event-schema/src/protocol/session.rs#L484-L496