Migrating to smoltcp 0.10 and add support for multiple interfaces

Migrating to smoltcp 0.10

This is a draft to show what it would take to update smoltcp to the latest version. I tested:

• Dhcp
• Ping with dns hostname
• Curl to some url
• git clone some repo
• nc -l 0.0.0.0:8080 to listen new tcp connection

It all work fine but sometime some ports stay occupied (with nc -l) for example.

They are maybe other regression to test and some of the fix needed to migrate are a bit hacky so i'll be glad to receive feedback from some dev of netstack

Add support for multiple interfaces

This draft also add support for multiple interfaces. We can now talk to 127.0.0.1 as well as on the ethernet. There is still a lot left to do :

• Add multiple interface support to netcfg because right now netcfg becomes a bit useless (Still hardcoded eth0 iface)
• Figure out how DHCP can configure the right interface (assuming configuring eth0 always)
• Fix latency having greatly increased (look at the polling strategy)
• Dynamically detect interfaces and remove hard coded network: scheme (In next MR)