Renovate Task architecture

[kanpov]

The current Task architecture has a few flaws that really need to be fixed.

• They aren't coroutines, which disables a lot of potential for the GUI
• They aren't applied everywhere, for example, Manager classes in the launcher
• They include 3 launch phases (prelaunch, launch and postlaunch), which aren't needed and increase complexity
• They use contexts as parameters due to the limitations of implementing an interface

This PR aims to fix all of these.

[kanpov]

This was easier than I thought it would be. Merging this PR and the only thing remaining to do before the vacation is modpack management in the next PR.