Check loading state with dependencies

[NiklasEi]

A handle should only be counted as loaded by this plugin when all it's dependencies are loaded.

count_loaded_handles should be using https://docs.rs/bevy_asset/latest/bevy_asset/struct.AssetServer.html#method.is_loaded_with_dependencies

[mgi388]

@NiklasEi I briefly tested that out 1 line change locally, looks to be working 😌

[mgi388]

The failure variable also needs to account for deps too otherwise if a dep fails to load the loading screen infinitely shows rather than transitioning to the error state.