Fixes#4137
Node identity is established when `STATE` partition is mounted, and
cached there. Node identity will be used for the cluster discovery
process to identify each node of the cluster.
Random 32 bytes encoded via base62 are used as node identity.
`base62` uses only URL-safe characters which might save us some trouble
later.
Signed-off-by: Andrey Smirnov <andrey.smirnov@talos-systems.com>
