Add `ingest_settings` property on metrics envelope container to infer IP addresses

[Lms24]

For Relay to infer IP and user agent data from the incoming trace_metric envelopes, the envelope must tell Relay that it should do this. This was spec'd out and agreed upon to happen in. the ingest_settings object on the trace-metric container (the metrics envelope item). See the spec for details.

Worth noting:

• This must only happen in browser SDKs!
• This is also relevant for logs (JS-2156) and spans (JS-2154)

[linear-code]

JS-2155