VolumeWiiCrypted: Replace ChangePartition with a partition parameter

By removing mutable state in VolumeWiiCrypted, this change makes
partition-related code simpler. It also gets rid of other ugly things,
like ISOProperties's "over 9000" loop that creates a list of
partitions by trying possible combinations, and DiscScrubber's
volume swapping that recreates the entire volume when it needs to
change partition.

Source/Core/Core/State.cpp

@@ -71,7 +71,7 @@ static Common::Event g_compressAndDumpStateSyncEvent;
 static std::thread g_save_thread;
 
 // Don't forget to increase this after doing changes on the savestate system
-static const u32 STATE_VERSION = 85;  // Last changed in PR 4241
+static const u32 STATE_VERSION = 86;  // Last changed in PR 2353
 
 // Maps savestate versions to Dolphin versions.
 // Versions after 42 don't need to be added to this list,