[steps] Expand legacy command/path local functions to a single build step

[sswrk]

Why

How

Test Plan

[linear-code]

ENG-25402

[sswrk]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [eas-cli] Validate legacy command/path local functions referenced from workflows #4098
• [build-tools] Load legacy command/path local functions and resolve module paths #4097
• [steps] Expand legacy command/path local functions to a single build step #4096 👈 (View in Graphite)
• [eas-build-job] Accept legacy command/path custom function shape in function.yml #4095
• [eas-cli][build-tools][steps] Validate local composite functions referenced from workflow hooks; extract the shared loader into steps #4064
• [build-tools][steps] Load composite function catalogs for hook steps #4063
• [steps] Support local composite functions in hook steps #4062
• [steps] Unify the default gating of steps with no if: across steps, composite scopes, and hooks #4061
• [eas-cli] Validate local composite functions in workflow files #3931
• [build-tools] Load local composite function catalog at build runtime #3930
• [steps][4/4] Resolve composite function outputs #4015
• [steps][3/4] Interpolate composite function inputs #4014
• [steps][2/4] Expand composite function references into build steps #3929 : 1 other dependent PR (#4013 )
• [steps][1/4] Add isCompositeFunctionPath and reject local composite functions in custom builds #3956
• [eas-build-job] Add local composite function schema #3928
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (szymonswierk/eng-25402-eas-build-job-legacy-function-shape@4ee8986). Learn more about missing BASE report.

Additional details and impacted files

@@                                      Coverage Diff                                      @@
##             szymonswierk/eng-25402-eas-build-job-legacy-function-shape    #4096   +/-   ##
=============================================================================================
  Coverage                                                              ?   62.72%           
=============================================================================================
  Files                                                                 ?      999           
  Lines                                                                 ?    45263           
  Branches                                                              ?     9508           
=============================================================================================
  Hits                                                                  ?    28388           
  Misses                                                                ?    15428           
  Partials                                                              ?     1447           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

⏩ The changelog entry check has been skipped since the "no changelog" label is present.