AI casts Exude Toxin with X = 0

**Describe the bug**
I raised this issue in #8836 among a couple of other things. I should've separated ea. of those things into its own separate issue. All apologies! I believe only the issue w/ the AI misusing a couple of lands was addressed. The issue is outlined @ the beginning of the linked thread & the rest of the thread can likely be ignored.

**To Reproduce**
Steps to reproduce the behavior:
1. AI is able to cast Scavenger Regent's Adventure for more than X=0 & prob should based on your board state.
2. You have a board state the AI could wreck using Scavenger Regent's Adventure.
3. Observe carefully.

**Expected behavior**
Toxins are harmful/fatal rather than amusing/annoying puffs of flatulence.

**Desktop (please complete the following information):**
- OS: Win 10
- 10.04 snap but it was prob on a previous albeit recent snap

**Additional context**
I saw another thread opened recently where AI is having difficulty using certain X spells. It seems like a really hairy problem because there are so many different X spells doing so many different things; there's no simple, catch-all logic that can have AI using X spells well in all circumstances. Is it really something where ea. X spell needs its own associated logic coded specifically for it??

From what I've seen, it looks like the AI does a before & after evaluation when analyzing combat outcomes. Perhaps something similar could be applied here as it pertains to X spells?? @ the least, if AI sees no significant benefit from using Scavenger Regent's Adventure @ X=0, it wouldn't do it. Altho I just thought of the situation where a player can use the Adventure repeatedly to prevent themselves from decking . . .