enhancement: vfs benchmarks

[barraguda]

Whenever we do a second passover of the vfs, we should actively benchmark something like sending big files.

app_store's internal ft_worker and file_transfer, among other implementations should be used. This might surface other inefficiencies in networking, smaller in-memory vfs calls like capabilities checking, but optimally we'd like to be at least on par with existing bittorrent/filesharing programs/libraries written in rust/others, like https://github.com/ikatson/rqbit.

Additional context
not necessarily a priority right now, but should be soon.