Going all-in with Netmiko #3937

I've been running device configuration with netmiko (wherever it's implemented) for a few weeks now, and it all seems to work, so it might be time to switch over:

• Make netmiko the default configuration method for Cisco IOS and Arista EOS (it's already the default method for IOS XR and Nexus OS)
• Make "copy shell scripts with netmiko, then execute them" the default method for Linux-based VMs (linux, frr)

Anyone who installed Ansible using netlab install ansible alread has netmiko installed, and I would make it a core requirement (or should I got for an optional requirement) in the next release.

Any objections/reservations/comments @sdargoeuves @DanPartelly @snuffy22 @Muddyblack @ssasso @jbemmel

Other work (I need to write down the checklist ;):

• netlab config must use netmiko where available
• netmiko should be used for the "are the interfaces ready" code (Nexus OS)
• I have to figure out how to do device configuration reloads.