test(nodejs): validate agentless EVP exposure egress

[leoromanovsky]

Motivation

Node.js agentless exposure delivery needs route-level coverage for direct and sidecar deployments.

Changes

• Activate Node.js direct and sidecar exposure egress coverage.
• Configure NODE_EXTRA_CA_CERTS for the mounted checked-in system-test proxy CA.
• Reuse the shared agentless scenario infrastructure from the Python system-test branch.

Decisions

• Preserve TLS verification through the system-test proxy.
• Assert direct EVP authentication with DD-API-KEY.
• Keep the draft stacked on leo.romanovsky/ffe-agentless-evp-fallback-python-tests for the shared direct-scenario infrastructure.

Validation

• Focused TEST_THE_TEST agentless-backend suite: 9 passed.
• Node.js Agent, direct, and sidecar focused runs: the exposure test passed in each topology.

Tracks FFL-1488.

[github-actions]

CODEOWNERS have been resolved as:

manifests/nodejs.yml                                                    @DataDog/system-tests-reviewers
utils/_context/_scenarios/agentless_endtoend.py                         @DataDog/system-tests-core

[datadog-datadog-prod-us1]

🎉 All green!

❄️ No new flaky tests detected

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[linear-code]

FFL-1488

[leoromanovsky]

Replaced by #7602 on the clean shared EVP egress base.