eqcompare: use C_Item.GetItemStatDelta for the comparison math

Replaces the twin-tooltip text extraction/comparison pair
(ExtractAttributes + CompareAttributes) with a single delta pull from
ClassicAPI's C_Item.GetItemStatDelta(equippedLink, newLink).

Base stats (Str/Agi/Sta/Int/Spi/Mana/Health + Armor + resistances) stay
annotated inline on their existing tooltip line: iterate the tooltip's
FontString regions (no more _G["...TextLeft"..i] name lookup), match the
"+N Foo" prefix, look up the trailing noun in a label→key map, append
(+delta)/(-delta) from the ClassicAPI delta table.

Extended stats (attack power / ranged AP / spell damage/healing / crit
ratings / hit ratings / mana regen / defense / DPS) don't emit their own
line — vanilla mixes them into equip-spell descriptions ("Equip:
Increases your critical strike chance by 1%") — so aggregate them into
a "Compared to equipped:" block at the bottom via AddDoubleLine. New
`tooltip.compare.extendedstats` config knob (default 1) gates that
block; it depends on `basestats` being on (its GUI checkbox grays out
otherwise). DPS rounded to one decimal — ClassicAPI derives it from
damage/delay so it lands as a raw float.

Random-suffix bonuses ("of the Bear" etc.) now count correctly since
GetItemStatDelta walks item-record + equip-spell auras + suffix
enchants server-side.

api/config.lua

@@ -752,6 +752,7 @@ function pfUI:LoadConfig()
   pfUI:UpdateConfig("tooltip",    nil,           "alpha",            "0.8")
   pfUI:UpdateConfig("tooltip",    nil,           "alwaysperc",       "0")
   pfUI:UpdateConfig("tooltip",    "compare",     "basestats",        "1")
+  pfUI:UpdateConfig("tooltip",    "compare",     "extendedstats",    "1")
   pfUI:UpdateConfig("tooltip",    "compare",     "showalways",       "0")
   pfUI:UpdateConfig("tooltip",    "vendor",      "showalways",       "1")
   pfUI:UpdateConfig("tooltip",    "questitem",   "showquest",        "1")