Clear suma discovery domain

[nelsonkopliku]

Description

This PR introduces domain logic to handle clearing up of software updates discovery results.
Basically when a user clears up suma credentials, whatever has been previously discovered, gets ignored.
Specifically the health of the software updates discovery gets ignored from the host's aggregated health.

This is going to happen in a loop for all the hosts meaning that a bunch of HostHealthChanged could be emitted upon creds clear up, with related ui notifications.

We could avoid these possibly many extra events by changing the aggregated health of a host silently when SoftwareUpdatesDiscoveryCleared, but meh... the host's health does change and it'd feel like we'd be missing something in the history.

How was this tested?

Automated tests

[dottorblaster]

LGTM

I was thinking maybe we could leverage already existing events but in the end it doesn't matter and when having events involved shortcuts fall short pretty quickly 👍