Add better damage prevention messages

[lostgeek]

Changelog

• Bugfix: Heartbeat was showing every card as facedown. Closes Heartbeat logs every trashed card as facedown #4307.
• Feature: Damage prevention now shows how much damage was prevented already. Closes Prevent damage should show the amount that was already prevented #4308.

[lostgeek]

Here's the new prevention in action (Heartbeat preventing one net damage):

Note: This behavior has been further changed. The prompt in the third image wouldn't even be displayed anymore.

[lostgeek]

A lot of broken tests, because the last commit removed the [Done] button on a lot of damage prevention prompts.

[NoahTheDuke]

Why change the damage prevention function to private? Seems like it doesn’t make things any clearer

[lostgeek]

I thought it might make it a bit cleaner, if I don't dump all that code into the damage-prevent function.

[NoahTheDuke]

Oh I see, I only looked at the commit diff, forgot to check the full diff. Yeah, you made the right call.