Verifies that enums in each of the platform-specific embedders, and the embedder API remain consistent with their API in dart:ui.

This tool is run as part of testing/run_tests.sh.

To run the tool, invoke with the path of the Flutter engine repo as the first argument.

../../../out/host_debug_unopt/dart-sdk/bin/dart \
  --disable-dart-dev                            \
  test/apicheck_test.dart                       \
  "$(dirname $(dirname $PWD))"