Performance CI missing real word regressions

[neilisfragile]

Is your feature request related to a problem? Please describe.

We use automated performance testing to track for regressions in Element X. These tests must be comprehensive to build confidence that the app is not slowing down as we add more functionality.

Describe the solution you'd like
I would like https://vector-im.github.io/element-x-ios/performance/ to be able to detect bugs like #2062 ahead of time. Or at the very least understand the failure mode to know why it is not possible.

[pixlwave]

A first guess at this given Matthew's hunch about key backups, the tests only sign in and log out. The client is never verified (so presumably backups aren't involved) and we never perform a subsequent launch verified or otherwise. Not sure how we would automate cross-signing with the current setup. Maybe these performance tests would be better to live in trafficlight (which I think supports multiple devices and so could cross-sign)?