Fix double refunding of organelle upgrade MP

[0HyperCube]

Brief Description of What This PR Does

When changing the organelle upgrade repeatedly in the same editor cycle, MP would be refunded twice (as detailed in #5524). This is because the cost of an upgrade also includes the negated cost of the current upgrade, meanwhile the editor refunds MP where ActionInterferenceMode.Combinable is returned as the interference mode.

I initially fixed this by not combining the actions. However I have now changed the implementation to avoid the negated cost.

Related Issues
Closes #5524

Progress Checklist

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• PR author has checked that this PR works as intended and doesn't
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  members reviewing this PR)
• 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.

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[dligr]

This PR fixes the issue based on my testing; the solution makes sense to me too.

[hhyyrylainen]

This fixes the infinite MP exploit (as long as I didn't accidentally mess up the steps). So I think this is good to merge now. I added a further TODO about a related issue that this doesn't fix (and I kept the deleted code as commented out for future reference).