Support variable substitution with odo build-images

[rm3l]

/kind feature

Which functionality do you think we should add?

I was trying to leverage odo to build and push images defined in a Devfile to my local registry, but this is currently not implemented.

$ odo build-images --var CONTAINER_IMAGE=localhost:5000/rm3l/mac-oui:`git rev-parse --short HEAD`
 ✗  --var-file and --var flags are not supported for this command

Why is this needed?

Just like odo deploy supports variable substitution when applying image components, odo build-images should be able to do the same thing, I think.

Variable substitution is helpful to pass values from the CLI without modifying the Devfile.
It should be possible to do the same thing with odo build-images to build images and push them to different registries for example.

This extends #5489.