[gce_test] Migrate from gsutil to gcloud storage and create InstallGcloudIfNeeded.

[franciscovalentecastro]

Since gcloud storage is now GA ¹ it is recommended to stop using gsutil. This may alleviate/fix some test flakes that occur when gsutil is installed or executed.

Followup to #456 , #457 by installing gcloud when missing in some distributions (e.g. sles-12, sles-15).

Testing in : GoogleCloudPlatform/ops-agent#2145.

b/462768459

Footnotes

1. https://docs.cloud.google.com/storage/docs/gsutil-transition-to-gcloud ↩

[avilevy18]

LGTM, I added a suggestion, but feel free to ignore it if you disagree.

[avilevy18]

I know this isn't part of the migration, but I think we should add another check to see if we have gcloud working now and fail if it can't call it.

Maybe lets factor out:

if _, err := RunRemotely(ctx, logger, vm, "sudo gcloud --version"); err == nil {
		// Success, no need to install gcloud.
		return nil
	}

into its own method.

[franciscovalentecastro]

I created verifyGcloudInstallation. I think it is valuable to log the installed gcloud version after the installation steps. Done.