Fix username code for ADE key retrieval

[Leseratte10]

There have been lots of reports of the error message "Failed to decrypt user key key (sic)" in the past. Looking at the source code, this error occurs when the Windows API call to CryptUnprotectData fails. This can happen if the entropy data is wrong.

ADE uses the Windows user name as part of that entropy data, and the script previously used the Windows API function GetUserNameW to retrieve the user's current user name.

However, this breaks when the user account has been renamed between ADE install and plugin usage. The key will be encrypted using the old name as entropy, but the python script will try to decrypt the key with the new current name, which will obviously fail.

Thankfully, ADE stores the user name (as it was at authorization time) in the registry - probably because ADE needs that info itself to access the key, so all that's needed to fix this is to read the user name from the registry instead of relying on Windows API.

This should be a proper fix (rather than the current workaround of "reinstall and re-authorize ADE") for #186, #252, #262, #278, #309, #348, #349, #371, #436, #471, #668, #708, #759, #815, #902, #1109, #1144, #1395 and #1938, all of which seem to be duplicates of eachother.

[mizuOda]

@Leseratte10 - Thanks for this!
FYI in case this isn't yet on your radar, @noDRM has forked this repo and is actively developing the plugin. Maybe worth a look at what they're doing? https://github.com/noDRM/DeDRM_tools

[Leseratte10]

Yeah, I've seen that repo but haven't looked at it too closely. If noDRM doesn't see (and merge) this PR on his own I'll post it over there, too, in a couple days. Or did you mean this in a way like "maybe the bug's already fixed in there"?

[mizuOda]

You probably already got notified, but noDRM merged your PR and released v10.0.2 with your fix today. Thank you.

Apprentice Harper also passed the torch to noDRM today and will no longer be maintaining this repo.