Fix IPL buildings leaking when the building pool is larger than 32768 - #5463

Summary

CIplStore::RemoveIpl finds an IPL's buildings through a 16 bit index range, so above 32768 slots it misses them and every stream-in adds another copy. Past that size it now scans the whole pool.

Motivation

Shrinking back is covered by #5462.

Test plan

crun engineSetPoolCapacity("building",100000) for i=1,(36000-engineGetPoolUsedCapacity("building"))/2 do createBuilding(1337,2900,-2900,0) end setElementPosition(localPlayer,-2150,200,40)
crun local t,p=0,{{-2150,200,40},{2050,1500,20}} setTimer(function() t=t+1 outputChatBox(t.." "..engineGetPoolUsedCapacity("building")) setElementPosition(localPlayer,unpack(p[t%2+1])) end,5000,8)

On master the count grows at every stop, with the fix SF and LV repeat the same numbers.

Checklist

• Your code should follow the coding guidelines.
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