Feature request: Add network interface filter

[aofei]

Describe the feature request

Add a network_names (string slice, the default is empty, and empty means all) configuration item to specify the network interfaces that need to be calculated by btm.

Usage:

network_names = ["eth0", "eth1"]

Additional context/details

At present, btm takes all network interfaces into consideration in traffic calculation. Of course, there's nothing wrong with it. But we must admit that there're some flaws in doing so. For example, there may be some network interfaces that people want to ignore, such as those created by docker. So it seems reasonable to add a network interface filter.

bottom/src/app/data_harvester/network.rs

Lines 33 to 37 in 0c21cba

	let networks = sys.get_networks();
	for (_, network) in networks {
	total_rx += network.get_total_received();
	total_tx += network.get_total_transmitted();
	}

[ClementTsang]

Yep, that sounds good. I plan on eventually allowing the ability to display per interface so this would tie nicely into that.