[Backport v1.27] Fix E2e tests on main

[dd-octo-sts]

Backport 6ef503a from #3064.

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What does this PR do?

• Use ECR registry instead of default registry.datadoghq.com to pull images faster on EC2: eeccc0d
• Run agent status ... -j with DD_LOG_LEVEL=off in k8s e2e checks so status output is clean JSON.
• Remove regex-based status JSON extraction and parse agent status -j output directly, failing when the command does not return valid JSON.

Motivation

The e2e assertions were compensating for log lines mixed into agent status -j output by extracting the first JSON-looking object. Disabling Agent logging for status commands makes the command output deterministic and lets the tests validate the actual JSON contract.

Additional Notes

No production code changes.

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: N/A
• Cluster Agent: N/A

Describe your test plan

• make lint-e2e

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label
• All commits are signed (see: signing commits)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.61%. Comparing base (1ad9264) to head (95e5523).

Additional details and impacted files

@@           Coverage Diff           @@
##            v1.27    #3068   +/-   ##
=======================================
  Coverage   41.61%   41.61%           
=======================================
  Files         336      336           
  Lines       28737    28737           
=======================================
  Hits        11958    11958           
  Misses      15984    15984           
  Partials      795      795           

Flag	Coverage Δ
unittests	41.61% <ø> (ø)

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🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 41.91% (+0.00%)

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