Adds a new device_info_app_build_configuration property to all events that can be:

• Debug: for local developer builds
• Alpha: for Release-alpha builds, I believe we use this for Installable Builds on PRs. This requires the app integrating the library to define an ALPHA preprocessor macro.
• Beta: for Release builds uploaded to TestFlight
• Production: for Release builds uploaded to the App Store

Alpha releases can be configured with the following in the app's Podfile:

  # Flag Alpha builds for Tracks
  # ============================
  installer.pods_project.targets.each do |target|
    next unless target.name == "Automattic-Tracks-iOS"
    target.build_configurations.each do |config|
      next unless config.name == "Release-Alpha"
      config.build_settings['GCC_PREPROCESSOR_DEFINITIONS'] ||= ['$(inherited)', 'ALPHA=1']
    end
  end

I've only implemented this for Woo in woocommerce/woocommerce-ios#4468, so I'm not sure if integrating this in WordPress will require any changes for the WP Internal builds.

Part of woocommerce/woocommerce-ios#4432

To test

1. Check out Include build configuration details in all tracks events woocommerce/woocommerce-ios#4468 and run the Woo app.
2. You can set a breakpoint in - [TracksServiceRemote sendBatchOfEvents:withSharedProperties:completionHandler:] and ensure that the properties argument contains Debug for device_info_app_build_configuration.
3. Check the Tracks Live View after a few minutes, and verify that the events coming from the app include the new property.

I haven't been able to test anything other than Debug builds yet 😞