Podman, Docker and toolbx cleanup.

The workbench image now the `docker` CLI, `podman-remote` and `podman`
symlinked to `host-spawn`. They all work out of the box without any
added configuration. So split the config to `.bashrc.d/`, replace some
aliases that use `docker` locally with `podman`, remove useless config,
add the `docker` contexts and replace aliases using `docker` remotely
with contexts.