Grafazos, Releases: Introduce a test release pipeline for Grafazos

What

This is a preliminary step toward the implementation of the new release process.

This merge request introduces a test release pipeline for Grafazos. This pipeline only contains a build job for now.

Next steps:

• Include a gitlab release
• Define this pipeline in grafazos/ci/releases/

Why

How

We introduce a file grafazos/ci/release.ml that defines the jobs used to release.

These jobs are included in the test pipeline defined in ci/bin/main.ml.

Manually testing the MR

See https://gitlab.com/nomadic-labs/tezos/-/pipelines/1748193992

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR