Stage Android emulator logcat output

[sjchmiela]

Summary

• stream adb logcat -v threadtime for every Android emulator started by eas/start_android_emulator
• write live logcat output to a well-known staging directory under the build logs directory
• record metadata for each stream so a later step can stop and collect logs safely

Why

When an Android emulator crashes before later diagnostics run, adb logcat -d may no longer work because the device is already gone. Streaming from startup preserves those logs without writing into directories that get archived.

Test plan

• cd packages/build-tools && yarn test startAndroidEmulator AndroidEmulatorUtils

[linear]

ENG-20762 Stream Android emulator logcat from the emulator start

[codecov]

Codecov Report

❌ Patch coverage is 81.25000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.50%. Comparing base (900ad76) to head (6c0f797).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ages/build-tools/src/utils/AndroidEmulatorUtils.ts	78.58%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3627      +/-   ##
==========================================
- Coverage   55.70%   55.50%   -0.19%     
==========================================
  Files         852      856       +4     
  Lines       36549    36826     +277     
  Branches     7642     7646       +4     
==========================================
+ Hits        20356    20437      +81     
- Misses      14774    16294    +1520     
+ Partials     1419       95    -1324     

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[github-actions]

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