Improve handling of IP addresses

[mydea]

Description

Today, we attach an IP address to the event if users opt-in to this via requestDataIntegration({ include: { ip: true } }). If this is enabled, we extract the IP address and add it to the event.

However, in scenarios where apps receive requests from a proxy, the IP address is often not the original IP address, but something like ffff:127.0.0.1. In this scenario, the "real" IP address can be found in a header.

We have code in relay that extracts these headers, if they are set, and sets the IP address based on this. Today, because of this we have two problems in the SDK:

1. If ip: true is configured in the SDK, we always set an IP address. Relay then never infers the IP from the headers, so we get the "wrong" IP address (e.g. the 127.0.0.1 one).
2. If ip: false, no IP will be set by the SDK, but if it is a proxy scenario the headers are today not filtered out, so relay will still infer this.

To fix this, we want to make two changes:

[ ] Look at headers in the SDK if ip: true is configured
[ ] Do not send these headers if ip: true is not configured

This way, we should have a more consistent outcome - either correct IP addresses is ip: true is opted-into, or else no IP addresses, no matter if it is a proxy/tunnel or not.

We can use these headers, which we currently look at in Remix:

• X-Client-IP
• X-Forwarded-For
• Fly-Client-IP
• CF-Connecting-IP
• Fastly-Client-Ip
• True-Client-Ip
• X-Real-IP
• X-Cluster-Client-IP
• X-Forwarded
• Forwarded-For
• Forwarded

[andreiborza]

We might want to include https://vercel.com/docs/edge-network/headers#x-vercel-forwarded-for in the list.