* synthetic packages by default in gen_l10n tool

* Refactor default path for synthetic package

* Remove unused import

* Code cleanup

* Further improvements to help text

* Refactor synthetic package path

* Remove newlines

* Test cleanup

* clean up logic in inputs and outputs list function

* Update l10n.yaml usage

* only add option if value is non-null

* Update stocks app as proof of concept for synthetic package usage

* Address nits

* print pubspec contents

* add print statements

* Do not allow null value for useSyntheticPackage

* +

* +

* +

* +

* Cleanup

* Add test

* Fix text

* Dont parse pubspec directly

* Test using context

* WIP: generate synthetic packages on pub get -- needs tests

* Allow null value

* Update null handling

* Refactor to properly handle null case

* Fix yamlMap condition

* Fix yaml node for real

* WIP: struggling to write tests

* WIP - take absolute path as an option

* Add tests

* Use environment project directory for synthetic package generation pathway

* Fix typo

* Improve help text

* Update defaults

* Remove unauthorized path import

* Fix pathing issues at synthetic package generation

* Fix typo in test

* Use path.join so projectDir matches up based on OS

* Fix Windows pathing in test

* Remove unnecessary replaceApp code for projectDir.path

* Use globals.fs.currentDirectory.path in resident_runner_test.dart

* Fix merge conflict

* Add test to ensure that synthetic package is generated on pub get

* Fix resident_runner_test.dart tests

* Fix tests

* Use package:file instead of dart:io

* WIP - exploration

* Remove synthetic package use from stocks example

* Update integration test to not use synthetic packages

* Remove trailing whitespace

* flutter pub get runs synth package generation

* Remove more print statements

* Add license header

* WIP - minimally working pub.get

* Use own MockBuildSystem

* Modify test and implementation to be a little cleaner

* Fix flutter pub get invocation

* Use synthetic packages in stocks app

* Revert "Use synthetic packages in stocks app"

This reverts commit 45bf24903c3d4a2a5fd5481d7d6bc36c4a348703.

* Add environment and buildSystem params to flutter test

* Address code review feedback

* +

* Isolate codegen into its own API

* Fix imports

* Slight refactor

* Add one more test for no l10n.yaml file

* Remove unneeded mock class and import in pub_get_test.dart

* More code review feedback

* Remove unnecessary imports

* Remove `return await`s that I missed

* use arrow functions instead