Rebalance Double membrane type

[Accidental-Explorer]

Brief Description of What This PR Does
For the "Double" membrane:

• Remove osmoregulation discount
• decrease health
• Increase toxin resistance

So the Double membrane is now a variant of "Normal" that sacrifices some speed for increased defense, but especially against toxins. (This is also effective against engulfed toxic cells).

This will also require a re-write of the tooltip, which I will do if/when the rest of the change is approved.

Related Issues

Double membrane type is a bit of a bland upgrade to Normal.

Desire among the community for more ways to counter toxins.

Progress Checklist

Note: before starting this checklist the PR should be marked as non-draft.

• PR author has checked that this PR works as intended and doesn't
  break existing features:
  https://wiki.revolutionarygamesstudio.com/wiki/Testing_Checklist
  (this is important as to not waste the time of Thrive team
  members reviewing this PR). This includes gameplay testing by the PR author.
• Initial code review passed (this and further items should not be checked by the PR author)
• Functionality is confirmed working by another person (see above checklist link)
• Final code review is passed and code conforms to the
  styleguide.

Before merging all CI jobs should finish on this PR without errors, if
there are automatically detected style issues they should be fixed by
the PR author. Merging must follow our
styleguide.

[hhyyrylainen]

I'll comment here while I still remember that Iman tested this and shared some feedback on Discord. I think the feedback was asking for further tweaks as this didn't yet seem ready.

[Accidental-Explorer]

I'll comment here while I still remember that Iman tested this and shared some feedback on Discord. I think the feedback was asking for further tweaks as this didn't yet seem ready.

Yes, I'm currently focusing on other PRs when I have time, but I can probably give this a tweak and give it another go. I'm thinking to increase Toxin resistance more, to really make it fill that role. But I might have to rebalance some other membrane types slightly to match.