Docker uses the term logging `driver` in its public documentations: in
`docker` daemon config[1], `docker run` arguments [2] and in docker compose file[3].
Interestingly, docker used `type` in its API [4] instead of everywhere
else.

It's unfortunate that Nomad used `type` modeling after the Docker API
rather than the user facing documents.  Nomad using `type` feels very
non-user friendly as it's disconnected from how Docker markets the flag
and shows internal representation instead.

Here, we rectify the situation by introducing `driver` field and
prefering it over `type` in logging.

[1] https://docs.docker.com/config/containers/logging/configure/
[2] https://docs.docker.com/engine/reference/run/#logging-drivers---log-driver
[3] https://docs.docker.com/compose/compose-file/#logging
[4] https://docs.docker.com/engine/api/v1.39/#operation/ContainerCreate