Make netplay's "same game" check more robust

Instead of comparing the game ID, revision, disc number and name,
we can compare a hash of important parts of the disc including
all the aforementioned data but also additional data such as the
FST. The primary reason why I'm making this change is to let us
catch more desyncs before they happen, but this should also fix
https://bugs.dolphin-emu.org/issues/12115. As a bonus, the UI can
now distinguish the case where a client doesn't have the game at
all from the case where a client has the wrong version of the game.

Source/Core/DiscIO/VolumeWii.h

@@ -92,6 +92,7 @@ public:
   bool IsSizeAccurate() const override;
   u64 GetRawSize() const override;
   const BlobReader& GetBlobReader() const override;
+  std::array<u8, 20> GetSyncHash() const override;
 
   // The in parameter can either contain all the data to begin with,
   // or read_function can write data into the in parameter when called.