Add Expo and packager command unit tests

[ConnorQi01]

Summary

• Add unit tests for ConfigEASBuild, Prebuild, KillPort, and EnableHermes commands.
• Cover Expo guard paths, command dispatch, port input handling, and Hermes Android/iOS file update branches.
• Keep the change scoped to tests only, following existing command test patterns with Sinon and proxyquire.

Validation

• npm test
• npm run build

Closes #2684