Add "best practices" section (such as updating workspace image) to gp rebuild log output

[loujaybee]

Currently doing gp rebuild on the first try takes a long time. We should emit some logs that warn users about best practices, such as not using workspace-full, due to it being potentially a lot slower to iterate on, and mention the other workspace images, such as workspace-base and other language based images as alternatives.

This would go well twinned with a docs update:

• https://github.com/gitpod-io/website/issues/2187

Relates to:

• The workspace-full takes a long time to docker pull in a first run of gp rebuild #16298

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.