feat: Support for the new packages folder

[0neGal]

When finished this'll both add support for the new packages/ folder discussed at NorthstarLauncher #505 and simultaneously it'll also add support for installing plugins properly, discussed at FlightCore #288.

This PR is far from complete, and it's only currently here for the sake of tracking progress.

TODO

• [x] Basic management of packages
  • [x] Enabling/Disabling packages
  • [x] Detect and install dependencies
  • [x] Remove older versions if they exist, i.e updating
  • [x] Move packages in mods/ to packages/ when updating
  • [x] Downloading, extracting, verifying and installing a package from a URL
  • [x] Present warning/confirmation dialog when installing a package with plugins
• [x] Implement everything in the frontend
  • [x] Toggling packages
  • [x] Removing packages
  • [x] Showing packages in the mod list
  • [x] Installing of packages through mod browser
  • [x] Updating of packages through mod list and mod browser
• [x] Localizations
  • [x] German - @DxsSucuk
  • [x] French - @Alystrasz
  • [x] Spanish - @AA-Delta

Strings that need to be localized:

"gui.mods.confirm_plugins_title": "The following package has native plugins:",
"gui.mods.confirm_plugins_description": "Native plugins have far more system access than a regular mod, and because of this they're inherently less secure to have installed, as a malicious plugin could do far more harm this way. If this plugin is one from a trusted developer or similar or you know what you're doing, then you can disregard this message completely.",