Match phys::System contact listener and group handler forwarders

[RobbyV2]

The FIXME'd _128 is indexed by ContactLayerType and its elements take ContactListener calls, so it is sead::FixedPtrArray<ContactListener, 2>, named mContactListeners; the bounds check in the assembly is sead::PtrArrayImpl::at.

freeLayerContactPointInfo drops the info's layer pairs from the listener for its layer type, then frees the info through ContactMgr. registerContactPointLayerPair adds one pair to that same listener. trackLayerPair selects the listener from the first layer's ContactLayerType and returns the ContactLayerCollisionInfo it tracks.

removeSystemGroupHandler indexes mGroupFilters by the handler's layer type and forwards to GroupFilter::removeSystemGroupHandler.

I added getLayerType to LayerContactPointInfo since mLayerType is private.

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This change is 

[Pistonight]

@Pistonight reviewed all commit messages and made 1 comment.
Reviewable status: 0 of 4 files reviewed, 1 unresolved discussion (waiting on RobbyV2).

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src/KingSystem/Physics/System/physSystem.cpp line 53 at r1 (raw file):

void System::removeSystemGroupHandler(SystemGroupHandler* handler) {
    mGroupFilters[int(handler->getLayerType())]->removeSystemGroupHandler(handler);

nit: prefer cpp cast static_cast<s32>(...) ( and other places )

[RobbyV2]

Done

[Pistonight]

Thanks for the PR!