Add a command to list supported drivers

[kschaab]

Need a way to call minikube to get a list of supported drivers on deployed system. This information comes back from help but is extremely difficult to reliably parse via regex and looks to contain temporal content (like experimental):
minikube start --help | grep -e "--driver='':"
--driver='': Driver is one of: virtualbox, parallels, vmwarefusion, hyperkit, vmware, docker, podman (experimental) (defaults to auto-detect)

This will aid us in fixing issue GoogleCloudPlatform/cloud-code-vscode#234.

[kschaab]

Would be really nice to also return the information from Suggest in pkg/minikube/driver/driver.go in the output from this command. Maybe this belongs as an option on the minikube options command since this command doesn't seem to do much at the moment. Something like minikube options list --command start --option driver. Alternatively this could be supported with --help with --output json but that seems quite complicated without knowing the code base.

[afbjorklund]

Someone was working on this (in #7679), but it seems to have stalled - we'll need to take over...

[afbjorklund]

It's equally stupid in the code base now, but should evolve into something nice from registry.

[afbjorklund]

@kschaab : the "options" command is like a side-effect of using the command framework. It's not really something that should be extended.

Use "minikube options" for a list of global command-line options (applies to all commands).

So this should probably use some kind of special JSON (or text?) output, similar to what we are doing for the progress output of minikube start

Like #8105

The easiest is probably doing it as an option to "start", even if that is a bit weird...

Another question is how much of the decision-making info we should dump
There's a side-project of building some kind of "smart" driver selection: #8012

So you could have reasons why a driver is or is not being selected at the moment.