[theseus] Add the ability to lock updates of a certain project on Instances

[EDM115]

Idk if this would be possible but the idea is that we can have a new action button on Instance -> Content (like a padlock icon) which will prevent a certain mod from receiving updates (even if we click on the Update all button)
The idea came when I made a custom instance which contains mostly client-side mods (which can be updated) and few server-side mods. These ones needs to stay on the version installed on the server to guarantee compatibility.
And I would like to update on one click all mods except some

The implementation on the GUI shouldn't be that hard

Behind the scenes, I see it like this :

• On the the profile.json there is a new required field for every project called lock_updates or so, which is a boolean that defaults to false. When set to true, theseus won't check for an update for this project, resulting in the Update all button not appearing if only locked projects have updates
• For backwards compatibility, for projects where this field doesn't exists, it's added with a false value

Optional things to implement :

• Add a way to filter the projects by their locked status (to easily unlock some on big instances)
• Maybe add a section in the global settings (or per-instance) that shows a warning everytime we wanna Update all, reminding us that some projects are locked (disabled by default)