ci: run the test suite under the race detector (PIPE-1223)

[Dylan-M]

Proposed Change

CI ran go test ./... with no -race, so data races in production code passed silently. This adds a make test-race target (go test -race ./...) and points the CI test job at it, with CGO_ENABLED=1 because the race detector needs cgo. make test stays unchanged for fast local runs.

The suite passes under -race; the data races it would otherwise catch are fixed in this stack.

How to validate

• Automated: make test-race runs the full suite under -race and passes (52 packages, no race reports).
• Manual: run make test-race locally, or review the workflow change.

Checklist

• Changes are tested
• CI has passed

[Dylan-M]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• ci: run the test suite under the race detector (PIPE-1223) #272 👈 (View in Graphite)
• fix(output): drain buffered records on TCP/UDP Stop (PIPE-1230) #271
• fix(count): fix Acquire/Reset data race in Tracker (PIPE-1231) #270
• fix(generators): own backoff timing in the worker to fix ExponentialBackOff data race (PIPE-1222) #269
• main

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