List all notes and show status note if any

[satterly]

[satterly]

@strangeman @vykulakov Please review. (Taken feedback from #228)

[satterly]

I'll merge this for now and iterate on it later if required.

[vykulakov]

Thank you for this improvement - it is really helpful and convenient now.

But I see two problems with the current approach:

1. I cannot edit/remove an old note. As a result, I must always see all notes which I left. Even those which are not actual now. In some cases, it may be helpful to see all alert notes, but in other cases, it will be confusing to see old unactual notes. It happens because you try to use alert history to store notes. But in my vision, they should be different and independent entities. So alert history should contain only changes in alert notes/state/status/severity and so on. And alert notes should contain all alert notes with a possibility to add/edit/remove them.
2. We won't see notes if there are more than 100 history records. It is very unexpected to suddenly lose all notes for an alert. It may happen for flapping alerts, for instance, or for alerts with a long history (which live years). The reason for this behaviour is also using alert history to store notes.

Nonetheless, status comments work fine and I don't see any obvious problems with them right now. We may lose the user's comment when alert severity is changing, though, but I'm not sure about it and should test this behaviour.

[vykulakov]

What I see (pay attention to comment content):

[satterly]

Thanks for the feedback. You have raised valid concerns. I'll keep track of this issue and will consider the improvements you have suggested in the near future. In the meantime, further comments and feedback are always welcome.

[satterly]

Discussion moved to #235