dsda: support the 2 known "fake" pwads that are actually iwads

fix #4340

add hacx and chex to db since they have canonical versions unlike the new stuff

Author: vadosnaprimer

Assets/gamedb/gamedb_doom.txt

@@ -134,3 +134,5 @@ ec5b38b30ba2b70e278205776af3fbb5		Freedoom: Phase 2 (v0.11.1)	Doom		Doom
 83560b2963424fa4a2eb971194428bf8		Freedoom: Phase 2 (v0.12.0)	Doom		Doom
 ca9a4159a7833544a89144c7f5053412		Freedoom: Phase 2 (v0.12.1)	Doom		Doom
 cd666466759b5e5f63af93c5f0ffd0a1		Freedoom: Phase 2 (v0.13.0)	Doom		Doom
+65ed74d522bdf6649c2831b13b9e02b4		Hacx - IWAD release (v1.2)	Doom		Doom
+25485721882b050afa96a56e5758dd52		Chex Quest	Doom		Doom

src/BizHawk.Emulation.Cores/Computers/Doom/DSDA.cs

@@ -60,7 +60,17 @@ public DSDA(CoreLoadParameters<DoomSettings, DoomSyncSettings> lp)
 				}
 				else if (wadFile.RomData is [ (byte) 'P', (byte) 'W', (byte) 'A', (byte) 'D', .. ])
 				{
-					_pwadFiles.Add(wadFile);
+					if (_fakePwads.Contains(GetFullName(wadFile).ToLowerInvariant()))
+					{
+						_iwadName = wadFile.RomPath;
+						_iwadData = wadFile.RomData;
+						foundIWAD = true;
+					}
+					else
+					{
+						_pwadFiles.Add(wadFile);
+					}
+
 					recognized = true;
 				}
 
@@ -346,6 +356,10 @@ private static bool PlayerPresent(DoomSyncSettings syncSettings, int port) =>
 		private readonly int[] _turnSpeeds = [ 640, 1280, 320 ];
 		private readonly string _dsdaWadFileName = "dsda-doom.wad";
 
+		// these are IWADs in terms of contents but they have "PWAD" in header
+		// source ports including upstream have special hacks to load them like IWADs
+		private readonly List<string> _fakePwads = [ "chex.wad", "rekkrsa.wad" ];
+
 		// order must match AspectRatio values since they're used as index
 		private readonly Point[][] _resolutions =
 		[