Beyond The End - Optimization and Fixes

    Fix GeckoLib 3 mob models going wild while the game is paused

    With the game paused, some GeckoLib 3 mobs (Dungeons Mobs' Blastling and
    other enderlings) spun their heads non-stop.

    GeckoLib 3.1.40 does not advance seekTime while paused, and
    AnimationProcessor#tickAnimation returns early when seekTime equals the
    previous one ("entity already animated on this tick"), so the bones keep
    last frame's values. Models that turn the head add to the bone's current
    rotation in setCustomAnimations (head.setRotationX(head.getRotationX() +
    headPitch)), so that addition piled up every frame.

    - New client mixin geckolib.AnimationProcessorPauseMixin (@Pseudo,
      remap=false): while paused, tickAnimation forgets the last seekTime
      (NaN), so the bones are recomputed every frame (same seekTime, same pose)
      and the head offset is applied on a clean pose. Nothing changes when the
      game is not paused.

    Fix GeckoLib 3 mobs jittering in GUI previews (JEI / Just Enough Resources)

    The mob previews of Just Enough Resources in JEI (and similar GUIs)
    jittered between poses (Mutant More, Dungeons Mobs...).
    AnimatedGeoModel#setCustomAnimations uses entity.tickCount + partialTick as
    the animation clock. Those preview entities are not in the world and never
    tick, so the clock only moved by the partial tick and jumped back every
    tick. JEI does not pause the game, so AnimationProcessorPauseMixin does not
    apply here.

    - New client mixin geckolib.AnimatedGeoModelGuiTickMixin (@Pseudo,
      remap=false, @Redirect on the Entity.tickCount read, SRG f_19797_):
      entities not added to the world use the client level game time instead.
      Entities in the world are unchanged.