Don't orphan pooled TF energy (Fixes shared TFE pool)

Attempt to fix #687 (closed).

Explanation/discussion in comment #687 (comment 492657499). Check my logic before approving. If there is a problem and it gets deployed, hopefully it will at least be simple to roll back.

A cursory test of the game with a reduced time before TFE gets pooled appeared to show expected behavior, but this was only a superficial test.

This change fixes the shared TFE pool. That is, it reinstates the behavior another change accidentally disabled without attempting to modify that original behavior. The effects of this may surprise some players as it means the TFE built on a victim by any attacker becomes usable by all attackers 3 hours after the original attacker's last cast in their attack, potentially giving some players a head start against their opponents if their victim has previously had that same spell cast against them. This could in particular affect NPCs: Dungeon demons, Minibosses, Narcissa, Mouse Sisters; and may be used tactically by PvP players. As a defense, players are encouraged to keep their willpower high at all times, and to cleanse away unspent Transformation Energy that has built up on them.

Fixes #687 (closed)