Draw the loot history and map overlays from real pools

Both modules had already grown a pool by hand. loothistory kept usedPlayers /
freePlayers tables with a recycle loop and a table.remove acquire; mapreveal
kept pfOverlays keyed by index, a pfOverlayMax high-water mark, and a
hide-the-tail loop. Replace both with ClassicAPI's Pools.lua backport, which
is what modules/tooltip.lua already uses for its buff icons.

The map explore icons change shape rather than just plumbing. Everything
constant -- size, scripts, mouse, frame level, the magnifying glass texture --
moves into the pool's creator instead of being re-set on every overlay on
every map update, and the acquire moves inside the visibility test. The old
loop built and configured an icon for every overlay in the zone and then hid
most of them again; with "mapexploration" off it built the whole set and hid
all of them. Now nothing is acquired for an icon that will not be shown.

The tile textures lose their pfRevealN names, since pools create anonymous
regions. They were already unique, so nothing was being clobbered -- this
only costs their labels in /fstack.

modules/loothistory.lua

@@ -104,7 +104,6 @@ pfUI:RegisterModule("loothistory", function ()
   -- Frame pools
   -- ==========================================================================
   local itemFrames = {}
-  local usedPlayers, freePlayers = {}, {}
 
   local FullUpdate -- forward declaration (toggle handlers call it)
 
@@ -204,20 +203,10 @@ pfUI:RegisterModule("loothistory", function ()
     return f
   end
 
-  local function RecycleAllPlayers()
-    for i = 1, table.getn(usedPlayers) do
-      local pf = usedPlayers[i]
-      pf:Hide()
-      table.insert(freePlayers, pf)
-    end
-    usedPlayers = {}
-  end
-
-  local function GetPlayerFrame()
-    local pf = table.remove(freePlayers) or CreatePlayerFrame()
-    table.insert(usedPlayers, pf)
-    return pf
-  end
+  local playerPool = CreateObjectPool(CreatePlayerFrame, function(_, pf)
+    pf:Hide()
+    pf:ClearAllPoints()
+  end)
 
   local function SetToggleTexture(toggle, isExpanded)
     if isExpanded then
@@ -309,7 +298,7 @@ pfUI:RegisterModule("loothistory", function ()
 
   function FullUpdate()
     if not pfUI.loothistory:IsShown() then return end
-    RecycleAllPlayers()
+    playerPool:ReleaseAll()
 
     local num = C_LootHistory.GetNumItems()
     local y = -2
@@ -327,7 +316,7 @@ pfUI:RegisterModule("loothistory", function ()
         for p = 1, f.numPlayers do
           local name, class, rollType, roll, isWinner, isMe = C_LootHistory.GetPlayerInfo(i, p)
           if ShouldDisplayPlayer(f.isDone, roll, isMe) then
-            local pf = GetPlayerFrame()
+            local pf = playerPool:Acquire()
             RenderPlayerFrame(pf, name, class, rollType, roll, isWinner)
             pf:ClearAllPoints()
             pf:SetPoint("TOPLEFT", list, "TOPLEFT", 22, y)