Match the original faint sound sequence per side (#709)

pokered plays no 'pitched-down faint cry': the player mon's faint is its
ordinary species cry (RemoveFaintedPlayerMon -> PlayCry) with no
Faint_Fall, and the enemy faint plays no species cry at all -- trainer
battles get SFX_FAINT_FALL then SFX_FAINT_THUD, wild battles go straight
to the victory music (FaintEnemyPokemon core.asm:732-796).

The port played the species cry AND Faint_Fall on every faint, so a
fainted enemy sounded its full battle cry and a fainted player mon got
the fall whistle the hardware never plays.

BattleState.onFaint now:
- player: Sound.playCry only
- enemy trainer: Faint_Fall then Faint_Thud (after the slide)
- enemy wild: no faint sfx (victory music already queued)

Adds tests/parity_faint_cry_bug709.lua asserting the per-side sequence.

Fixes #709

src/battle/BattleState.lua

@@ -3540,8 +3540,16 @@ function BattleState:onFaint(battler)
   self:actNext(function()
     battler.fainted = true
     local Sound = require("src.core.Sound")
-    Sound.playCry(self.data, battler.mon.species)
-    Sound.play(self.data, "Faint_Fall")
+    if battler.isPlayer then
+      -- RemoveFaintedPlayerMon (core.asm:1040-1042): the player mon's
+      -- faint plays its ordinary species cry -- no Faint_Fall
+      Sound.playCry(self.data, battler.mon.species)
+    elseif self.kind ~= "wild" then
+      -- FaintEnemyPokemon (core.asm:732-771): the enemy faint plays no
+      -- species cry; trainer battles get SFX_FAINT_FALL, then SFX_FAINT_THUD
+      -- once it finishes (wild battles skip straight to the victory music)
+      Sound.play(self.data, "Faint_Fall")
+    end
     self.fx = self.fx or {}
     -- SlideDownFaintedMonPic: PIC_HEIGHT (7) slide steps, each closing with
     -- DelayFrames 2 (core.asm:1186-1222).  The port held this one twice as
@@ -3550,6 +3558,13 @@ function BattleState:onFaint(battler)
   end)
   self.nextInsert = (self.nextInsert or 0) + 1
   table.insert(self.queue, self.nextInsert, { wait = Timing.FAINT_SLIDE })
+  if not battler.isPlayer and self.kind ~= "wild" then
+    -- FaintEnemyPokemon's SFX_FAINT_THUD lands as the slide does (after
+    -- Faint_Fall, before EnemyMonFaintedText)
+    self:actNext(function()
+      require("src.core.Sound").play(self.data, "Faint_Thud")
+    end)
+  end
   if not battler.isPlayer and self.kind == "wild" then
     -- FaintEnemyPokemon .wild_win (core.asm:792-795): beating a wild
     -- mon calls EndLowHealthAlarm and starts MUSIC_DEFEATED_WILD_MON