Use Arktos-vm-runtime instead of virtlet in runtime surface areas

[yb01]

What:
Replace virtlet with Arktos-vm-runtime in logging, config file folder, config, demo scripts etc.

Why:
Even the Arktos-vm-runtime is started from Virtlet code base, since we declared it as new product as Arktos-vm-runtime in the new repo, we shall use Arktos-vm-runtime, instead of virtlet, in the key surface areas, such as log, config folder, config entries etc as a minimum effort. some internal areas, such as code base, can leave as it for now.