Hull no longer depends on FightSystem: plugin, world, region, ground
visibility and hidden blocks are passed in. HullRegion is the common block
box hulls work on. The generic HullHider<K> manages one hull per key and does
the block, entity and REntity tracking; FightHullHider keeps the fight
specific parts (team hulls, viewer rules, state dependent registration).
Entities are now checked against the hull with block coordinates, so entities
in the bottom layer and at the max z edge are handled correctly.
HiderCore holds the TechHider, ChunkHider and AccessPrivilegeProvider so that
FightSystem and BauSystem can both shade it. BlockIds and ProtocolUtils stay in
SpigotCore (used by AntiNocom and RFallingBlockEntity) and move to
de.steamwar.core to avoid a split package. The access widener entries the
TechHider needs are duplicated into hidercore.accesswidener; the legacy
TechHider still needs its own copies in SpigotCore.