Engineering career dev matrix for Associate

Why is this change being made?

Adding the Associate career development matrix for Engineering.

1. This new career matrix for Associate is based on the Intermediate matrix.
2. Follow-up MR(s) can be added to extend or override per Department within Engineering.

To review, compare the Associate and Intermediate pages.

• Associate (review app) https://eng-career-dev-matrix-associate.about.gitlab-review.app/handbook/engineering/career-development/matrix/engineering/associate/index.html
• Intermediate (in production) https://about.gitlab.com/handbook/engineering/career-development/matrix/engineering/intermediate/

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
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  • The when to get approval handbook section explains the workflow in more detail
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

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