Implement Tera Shell

[jaimefd]

Implemented the ability Tera Shell.

Added FullHpTypeMultiplierAbAttr that changes the type multiplier when defending if the user was full HP at the start of the turn.

Had to create a boolean called "startedFullHp" since Tera Shell isn't like Multiscale. If you get hit by a multi-hit move, all hits are reduced if you were full HP at the start of the attack.

There may be better ways to implement this, so let me know if I can improve it in any way.

[Xavion3]

Also there's some merge conflicts to fix.

[jaimefd]

Changes from the previous version of the PR:

• Updated the description at the top of the PR with the new template
• Cleaned up the logic a bit, with inspiration from https://github.com/pagefaultgames/pokerogue/pull/728, renaming the attribute to ReceivedMoveEffectivenessAbAttr and making it extend PreDefendAbAttr for consistency with the existing ReceivedMoveDamageMultiplierAbAttr
• Added some documentation for the attribute
• Reworked the logic that checks if the target was full HP at the start of the hits. It no longer updates it both at the start and end of the hits, it only does it at the start, as the other one was unnecessary. It now also keeps track of the HP before the attacks, instead of being a boolean, to potentially make it useful in the future.

[flx-sta]

No action within more than a month. Considered stale