Account For More Edge Cases

[dotaxis]

A few users have been popping up with issues that most people don't have. Fixes have been applied for those scenarios

• Sometimes a symlink pointing to the current directory will exist inside the FF7 install path. I believe this is leftover from the very old Bottles installation method. Having this symlink present will cause 7th Heaven to go into an infinite loop on the "Verifying installed game is compatible" step of launching the game. 7thDeck will now remove this symlink to avoid this problem.
• Some users will receive an error installing vcredist and/or dotnetdesktop7 using the 7th Heaven installer. Thanks to infirit the cause for this has been discovered, and a fix has been applied.
• Some users with a native version of .NET installed on their system will have 7th Heaven try to load that instead of the .NET Desktop version installed in the proton prefix. 7thDeck will now unset the $DOTNET_ROOT variable and remove /home/deck/dotnet from $PATH when launching 7th Heaven. Some slight tweaking to this fix needs to be completed before this PR can be merged.
• The detection of proton prefixes on the Steam Deck's SD card has been reworked to check all directories under /run/media/deck/ instead of relying on the symlink at /run/media/mmcblk0p1. I am not sure how long Valve plans to keep the symlink there, but this change has been made in the interest of future proofing. This requires some testing before this PR can be merged.

[dotaxis]

Some updates

• The change to $PATH has been tweaked to expand the $HOME variable instead of checking for /home/deck/dotnet. This should mean the fix will also apply to those not on SteamOS.
• The check for proton prefixes on the Steam Deck's SD card has been removed entirely. This is because in order for the prefix to actually be recognized by Steam it must be symlinked in the ~/.steam/steam/steamapps/compatdata folder, so it will always be accessible there.
• Wiping of the prefix has been tweaked to only remove the contents of the folder instead of deleting the folder itself. This way, if the prefix folder IS symlinked to the SD card, that link will be preserved when the prefix is rebuilt by Steam.