Add support to tar flag for docker scan

[guyshe-jfrog]

• The pull request is targeting the dev branch.
• The code has been validated to compile successfully by running go vet ./....
• The code has been formatted properly using go fmt ./....
• All static analysis checks passed.
• All tests have passed. If this feature is not already covered by the tests, new tests have been added.
• All changes are detailed at the description. if not already covered at JFrog Documentation, new documentation have been added.

Part of jfrog/jfrog-cli#2451

[attiasas]

1. Change the description and name of the Argument, now that it is not only a tag (at cli/docs/scan/dockerscan/help.go)

2. Add integration tests that runs scan on .tar file

[attiasas]

Suggested change

	if dsc.progress != nil {
	dsc.progress.SetHeadlineMsg("Creating image archive 📦")
	}
	log.Info("Creating image archive...")
	dockerSaveCmd := exec.Command("docker", "save", dsc.imageTag, "-o", imageTarPath)
	var stderr bytes.Buffer
	dockerSaveCmd.Stderr = &stderr
	err = dockerSaveCmd.Run()
	if err != nil {
	return fmt.Errorf("failed running command: '%s' with error: %s - %s", strings.Join(dockerSaveCmd.Args, " "), err.Error(), stderr.String())
	if dsc.progress != nil {
	dsc.progress.SetHeadlineMsg("Creating image archive 📦")
	}
	log.Info("Creating image archive...")
	dockerSaveCmd := exec.Command("docker", "save", dsc.imageTag, "-o", imageTarPath)
	var stderr bytes.Buffer
	dockerSaveCmd.Stderr = &stderr
	err = dockerSaveCmd.Run()
	if err != nil {
	return fmt.Errorf("failed running command: '%s' with error: %s - %s", strings.Join(dockerSaveCmd.Args, " "), err.Error(), stderr.String())

You can move it to a separated method to help with readability

[attiasas]

Why you need it in audit command? this is just for docker scan....

[attiasas]

You can use the scan command to scan binary