Consistent terminology and more ovbious deploy failure on task page

[Calvinp]

This includes several UI improvements around task and deploy failures:

On the task page:

• Healthcheck failed notification now states that the task was killed, rather than task failed
• If the healthcheck failed because a connection was refused, the healthcheck failed notification will state that it was probably a problem with the app, not the cluster
• The healthcheck notification will not display if the deploy failed and killed the task after one healthcheck ran and failed (but not enough to kill the task)
• If this task caused the deploy to fail, it will have a danger notification saying this (and linking to other causes)
• If this task's deploy failed, but this task was not a cause of that failure, then it will have a warn notification. This notification will state if the task was killed because the deploy failed, and it will link to failure causes.

On the deploy page:

• Rather than say (n) tasks failed, now the message states how many causes of deploy failure there were. Those two numbers don't always match and caused some confusion.
• The links to the tasks that failed will now have the taskIds bolded to make it more clear that they are links to the task pages.

[ssalinas]

Doesn't look like this method is used. You can probably eliminate the section below where it is calculated in renderData and just use this

[Calvinp]

I was getting errors using the function at first, but it seems to be working now so I'll use the function.

[Calvinp]

A task's failed healthchecks caused its deploy to fail. There weren't enough failed healthchecks to fail the task, but there were enough to fail the deploy. This then caused the task to be killed.

It is probably appropriate to show the healthcheck notification in this edge case. It is not being shown right now because this PR doesn't show the notification when the failing deploy caused the task to fail. Maybe if this task is one of the deploy failure causes, show the healthcheck notification anyway. That might cause other edge case failures (task triggers a deploy failure for some reason other than failing healthchecks -> deploy fails -> task killed), but I'm not sure how to detect and account for all possibilities.

[ssalinas]

This has been looking good, messaging is much more clear, thanks @Calvinp