[infra] Cancel EAS runs when system-tests workflow is canceled

[sjchmiela]

Why

• Canceling the GitHub Actions workflow should cancel the underlying EAS build/workflow runs to avoid wasting resources.

How

• Start the iOS build and Android workflow with --no-wait and capture their IDs from JSON.
• Poll the EAS build/workflow statuses to determine success/failure.
• Persist IDs to GITHUB_ENV and cancel them in a if: cancelled() step.

Test Plan

https://github.com/expo/eas-cli/actions/runs/20859556010/job/59935355509

[github-actions]

Size Change: +629 B (0%)

Total Size: 53.3 MB

Filename	Size	Change
./packages/eas-cli/dist/eas-linux-x64.tar.gz	53.3 MB	+629 B (0%)

_{compressed-size-action}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.61%. Comparing base (3a7182b) to head (818e3ca).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3298   +/-   ##
=======================================
  Coverage   49.61%   49.61%           
=======================================
  Files         671      671           
  Lines       27972    27972           
  Branches     5780     5780           
=======================================
  Hits        13876    13876           
  Misses      12906    12906           
  Partials     1190     1190           

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[github-actions]

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[github-actions]

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