Allow the Docker socket to be configured as an optional parameter to the docker-type blocks in the config

[mieubrisse]

Background & motivation

To solve #1072 and #1140 , #1362 was implemented.

However, this is hacky: it requires setting a magic DOCKER_HOST environment variable, which the user needs to know exist. Additionally, it means that Kurtosis is no longer self-contained: it will be reading an environment variable that the user may or may not have set (and the user needs to set in their .bashrc).

Desired behaviour

Kurtosis should be completely self-contained, meaning all Kurtosis settings are read from Kurtosis configs, and the Docker socket should be configurable in the Kurtosis config file. Kurtosis should not read the DOCKER_HOST environment variable.

Kurotsis' new preference algorithm should be:

1. Use the socket set in the config block as detailed in Support DOCKER_HOST environment variable #1072 (comment)
2. Use the system wide docker socket /var/run/docker.sock if it exists
3. Use the user docker socket ${HOME}/.docker/run/docker.sock if it exists
4. Fallback to docker.FromEnv

Additionally, we have docs on how to set this in the Kurtosis config file.

How important is this to you?

Painful; the lack of this feature makes using Kurtosis frictionful.