Update to Godot v4

[otDan]

A few things got changed like Pool into Packed and stuff, I tried looking into it but it seems that it needs a deeper rewrite.

[jellehermsen]

First up is making sure gdunzip works in Godot 3.5. Version 4 will indeed require more work. However, there might be new zip functionality coming up, so it's best to wait how that pans out when they freeze the features for that release.