Normalize http.response.status_code for Metrics & Alerts

[AbhiPrasad]

Problem Statement

ref #8365
team issue getsentry/team-sdks#9

Add status code to transactions under contexts.response.status_code

Response context: https://github.com/getsentry/relay/blob/master/relay-general/src/protocol/contexts/response.rs

Solution Brainstorm

Add context on transaction.finish

Add types for response context

[mydea]

Just to clarify, this is not fixed by #8366, but in addition to that we also want to set the status code in the transaction context?

[AbhiPrasad]

Yes, because transactions don't have data applied to them.

[mydea]

This PR: #14634 should fix this - at least for transactions, we do not need to care about metrics there I guess.