refactor file dropping to use a single Vec instead of two

[Bonsix]

A change that I noticed could be done in file dropping. There's two Vecs related to dropped files, one for storing the paths and the other for storing the bytes of the files. I thought that having this done as a single Vec of a new DroppedFile struct containing both the path to the file and the bytes of the file is probably a more obvious way of doing this, instead of having two separate Vecs that are ultimately still connected. It also allows for easier further changes, as now you can work with the entire file structs instead of needing to worry about whether or not the Vecs actually match in content counts (which they should always do)