Add Intermediate and Senior Distribution career matrix items for Enablement

Why is this change being made?

To provide clear expected competencies for Distribution Engineers by adding Enablement and Distribution sections to the engineering career matrix.

This adds Enablement as a section with a matrix. And then Distribution as one of the roles within the Enablement matrix. (Additional roles might be Backend Engineer, Frontend Engineer, Fullstack Engineer, Database Engineer, etc)

Distribution Engineers are currently holding a different title than Backend engineers in bamboo, so keeping them separate for now.

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