feat: add ability to not auto update into a marked version

[brandonskiser]

Description of changes:

• Adding the ability to tag versions in the index.json as not being able to be auto-updated into, and updating the client to not auto-update into these tagged versions.
• Updating the "Check for updates..." tray button to now ask for permission to update before updating - currently, we will automatically update when one is available (this matches the same behavior as Linux AppImage).

The only point where we actually auto-update is at the desktop app launch. Otherwise, we will always update as normal (e.g. with q update)

Example index.json entry

"versions": [
    ...,
    {
      "version": "1.19.4",
      "packages": [
         ...
      ],
      "disable_autoupdate": true
    }

Testing

Tested by creating local builds and using a test index.json endpoint.

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