[build-tools] Upload embedded bundle by default on SDK 58+ and rename env var

[brentvatne]

Why

Uploading the embedded bundle after an EAS Build lets EAS Update serve bsdiff patches to fresh installs on their very first update check. It has been opt-in behind EAS_UPDATE_EXPERIMENTAL_UPLOAD_EMBEDDED_BUNDLE. This makes it the default for projects on SDK 58 and later, controlled by a non-experimental env var, while keeping it experimental and opt-in on SDK 57 and below.

How

• When no env var is set, shouldUploadEmbeddedBundle falls back to metadata.sdkVersion and enables the upload only for SDK >=58. An unknown SDK version leaves it off.
• SDK 58 and later: set EAS_UPDATE_UPLOAD_EMBEDDED_BUNDLE to 0 (or false) to disable the upload.
• SDK 57 and below: the feature is still experimental. EAS_UPDATE_EXPERIMENTAL_UPLOAD_EMBEDDED_BUNDLE=1 remains the supported opt-in, with no deprecation warning.
• Both the Android and iOS builders call the new helper instead of checking the env var directly.

Docs: expo/expo#50307

Test Plan

Unit tests in packages/build-tools/src/builders/__tests__/android.test.ts cover: default on for SDK 58, default off for SDK 57 and for unknown SDK, explicit 1 on SDK 57, explicit 0 on SDK 58, and the experimental var on SDK 57.

yarn jest-unit src/builders/__tests__/android.test.ts src/utils/__tests__/expoUpdatesEmbedded.test.ts
Test Suites: 2 passed, 2 total
Tests:       27 passed, 27 total

yarn lint and tsc pass.

Checklist

• I added a changelog.md entry
• Tests added / updated

🤖 Generated with Claude Code

[brentvatne]

Docs: expo/expo#50307

[github-actions]

✅ Thank you for adding the changelog entry!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.30%. Comparing base (c7b3105) to head (2a5f042).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4433      +/-   ##
==========================================
+ Coverage   72.29%   72.30%   +0.01%     
==========================================
  Files         970      970              
  Lines       46133    46145      +12     
  Branches     9903     9909       +6     
==========================================
+ Hits        33349    33361      +12     
  Misses      11789    11789              
  Partials      995      995              

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[gwdp]

LGTM, Thank you for doing it!