[Launcher] Check for disabledPackageSources (in NuGet.config)

Release Type: Official Release

Version: Xenko Launcher 3.0.1

Platform(s): Windows

Describe the bug Because Xenko Launcher doesn't check for disablePackageSources in NuGet.conf, if the xenko nuget packages are disabled, the xenko launcher will think it's offline and won't be able to connect to the internet to download the xenko builds from the internet

To Reproduce Steps to reproduce the behavior:

1. open NuGet.config in %APPDATA%\NuGet\NuGet.config
2. add these lines in configuration

<disabledPackageSources>
    <add key="Xenko" value="true" />
    <add key="Xenko Dev" value="true" />
  </disabledPackageSources>

3. The Xenko launcher cannot connect and download xenko builds

Expected behavior The launcher should check if the xenko package are disabled and automatically enable them, or ask the user the authorization to enable them

Screenshots