[userland] Put app icons paths into info.json

[neutrino2211]

App icons are currently saved as part of the base system in /res but can be made relative, similar to exec_rel_path.

I'm thinking of using a Resources folder in the application source directory and an info.json file that can override some of the definitions in the userland build prepare_app.py script which writes the built application's info.json, that way, an icon_rel_path variable can be declared there which could be used by the system.

[espero-dev]

@neutrino2211 what os are you building it on im on ubuntu 23.0 core i5 8th gen nvidia and i cant build it