Create Docker image with only the CLI

### Is your proposal related to a problem?

Users who need to use the Hasura CLI may spend time creating custom images, troubleshooting version compatibilities, local machine conflicts or require ephemeral images for CI/CD.

### Describe the solution you'd like

An official Docker image with the Hasura CLI only.

### Describe alternatives you've considered

Using the CLI-migrations image is both heavier and more complicated than necessary due to the bundling of Hasura GraphQL engine and the renaming of the binary from the default `hasura` to `hasura cli`.

Start by reviewing the existing CLI-migrations image and how the Hasura CLI binary is packaged and invoked. The work is done when an official Docker image contains only the CLI, uses the default hasura binary name, and is suitable for ephemeral CI/CD use.

Written by the indexing model from the issue text.