Add Datadog code coverage upload

[ManuelPalenzuelaDD]

What does this PR do?

We're migrating Datadog repositories from Codecov to Datadog Code Coverage for tracking test coverage. This PR is the first step: it adds a Datadog coverage upload alongside the existing Codecov upload so we can run both systems in parallel and verify parity before switching over.

Changes

• Added DataDog/coverage-upload-github-action@v1 step to the build job in validation.yml, running after the existing Codecov upload
• Added code-coverage.datadog.yml with ignore paths (test/, **/zz_generated.*.go) and 80% patch coverage gate mirroring the Codecov config
• Coverage format: Go Coverprofile (cover.out) with unittests flag (mirroring Codecov)
• The existing Codecov uploads are unchanged — nothing is removed or modified
• The upload uses if: always() and continue-on-error: true so it cannot block CI

Why are we doing this?

As part of a company-wide effort, we're consolidating code coverage reporting into Datadog's own Code Coverage product. This gives us:

• Coverage data integrated directly into Datadog CI Visibility
• PR gates and coverage checks natively in Datadog
• No dependency on a third-party service (Codecov) for coverage reporting

Validation

Pending — requires DD_API_KEY secret to be configured in this repo. Coverage comparison will be possible once the secret is added.

Next steps (not in this PR)

Once this PR is merged and we've confirmed Datadog coverage is stable over several commits:

1. Remove the Codecov upload steps and CODECOV_TOKEN secret
2. Remove codecov.yml
3. Optionally configure PR gates in code-coverage.datadog.yml

No action needed from reviewers beyond normal review

This is a low-risk, additive change. The new upload step runs independently of the existing CI pipeline and cannot cause test failures.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 37.96%. Comparing base (ee9b77e) to head (d6612ea).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #267   +/-   ##
=======================================
  Coverage   37.96%   37.96%           
=======================================
  Files          65       65           
  Lines        3856     3856           
=======================================
  Hits         1464     1464           
  Misses       2276     2276           
  Partials      116      116           

Flag	Coverage Δ
unittests	37.96% <ø> (ø)

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