Prior to this commit, the build plugin goal/task for building images
required a locally running Docker daemon that was accessed via a
non-networked socket or pipe.

This commit adds support for remote Docker daemons at a location
specified by the environment variable `DOCKER_HOST`. Additional
environment variables `DOCKER_TLS_VERIFY` and `DOCKER_CERT_PATH`
are recognized for configuring a secure TLS connection to the daemon.

Fixes gh-20538