Process disk rw

[GuillaumeGomez]

Taking over #248.

cc @bvaisvi

On windows, the performance are still miserable. An alternative could be to use GetProcessIoCounters, however it returns all I/O (so disk+network+driver, whatever "driver" means). So to get a somewhat accurate information, it'd require to get the network usage for the process and subtract it from what GetProcessIoCounters returns. Quite annoying... As a result, windows performance is getting 3 times worst when adding new process:

test bench_new                     ... bench:   7,918,095 ns/iter (+/- 422,384)
test bench_new_all                 ... bench:  92,207,290 ns/iter (+/- 6,613,951)
test bench_refresh_all             ... bench:   1,561,685 ns/iter (+/- 132,639)
test bench_refresh_components      ... bench:           1 ns/iter (+/- 0)
test bench_refresh_components_list ... bench:      28,625 ns/iter (+/- 1,849)
test bench_refresh_cpu             ... bench:      34,676 ns/iter (+/- 9,526)
test bench_refresh_disks           ... bench:      56,971 ns/iter (+/- 2,548)
test bench_refresh_disks_lists     ... bench:     125,932 ns/iter (+/- 4,918)
test bench_refresh_memory          ... bench:       1,042 ns/iter (+/- 28)
test bench_refresh_networks        ... bench:      39,778 ns/iter (+/- 3,216)
test bench_refresh_networks_list   ... bench:   1,374,947 ns/iter (+/- 58,170)
test bench_refresh_process         ... bench:       1,288 ns/iter (+/- 125)
test bench_refresh_processes       ... bench:   1,135,397 ns/iter (+/- 254,835)
test bench_refresh_system          ... bench:      38,371 ns/iter (+/- 7,019)
test bench_refresh_users_list      ... bench:   3,427,415 ns/iter (+/- 108,865)

The only way I found to reduce this performance drop even more is to only compute disk usage when user requests it (otherwise, it's 70 times slower!!!).

[bvaisvil]

Great to see this get added!