GitLab Pipelines tracing prototype to inform Trace semantics

[adrielp]

Overview

Build out the GitLab Actions tracing prototype using current & potentially future semantic conventions. This will also provide implementation context on the Environment Variable specification. As this prototype is created and operational, the semantic conventions will be updated accordingly.

Note: This could become an exceedingly large piece of work. Will break down into tasks, and find a balancing line between creating new issues.

• create trace skeleton
• create data model with current attributes
  • pr data model to semconv
• get functional

[adrielp]

CC. @niwoerner

I can't assign it to you because I think you've not interacted with this repository yet, but I'm going to CC you in the issue and leave it assigned to me.