Fetch the user's device info before processing a verification request (#5030)
* Use checked way to get OlmMachine
* Factor out two variables in onKeyVerificationEvent
* Make sure verification test waits for the request to be processed
* Fetch the user's device info before processing a verification request
If we don't have the device info for a user when we receive their
verification request, we ignore it. This change gives us the best
possible chance of having the right device data before we try to process
the verification.
Fixes #30693
Fixes #27819