feat: add support for remote docker over ssh

[catusax]

Fixes: #5703

Description
this pr adds support for remote docker over ssh using connhelper package, the feat was introduced by docker cli by this commit: docker/cli#1014

TestCase

open google cloud shell:

https://ssh.cloud.google.com/cloudshell/editor?cloudshell_git_repo=https://github.com/catusax/skaffold&cloudshell_git_branch=docker-ssh-support&cloudshell_open_in_editor=examples/cross-platform-builds/skaffold.yaml

# setup ssh
ssh-keygen
cat ~/.ssh/id_rsa.pub > ~/.ssh/authorized_keys
chmod 640 ~/.ssh/authorized_keys
sudo service ssh restart
ssh-copy-id 127.0.0.1
export DOCKER_HOST=ssh://127.0.0.1

# setup docker
export DOCKER_USER=<your dockerhub userid>
docker login -u $DOCKER_USER

export ROOT=$PWD && export PROJECT=$ROOT/examples/cross-platform-builds
cd $PROJECT

sed -i 's/skaffold-example/${DOCKER_USER}\/skaffold-example/g' skaffold.yaml
skaffold build # this will fail
# Cannot connect to the Docker daemon at ssh://127.0.0.1. Is the docker daemon running?. Docker build ran into internal error. Please retry.
# If this keeps happening, please open an issue..

# build new patch
cd $ROOT && LOCAL=true make 
sudo cp out/skaffold /usr/bin/skaffold

# build with ssh support
cd $PROJECT
skaffold build # success

# without ssh
unset DOCKER_HOST
skaffold build # success

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[catusax]

sry for the unit test failure,i have fixed it

[aaron-prindle]

@catusax thank you very much for the PR here adding this feature and the detailed info you added here. Just tried it out, works great! LGTM!

[aran]

Cross-referencing this issue here: #9484

Not sure if this is still working for you @catusax?

From a quick look at docs, it looks as if the latest Go docker client libraries may natively support ssh connections, so one path might be to remove this and upgrade the dependency.