This implements the `DartDependencySetBuilder` completely in Dart instead of calling out to `sky_snapshot` (Linux/Mac) or `gen_snapshot` (Windows) and allows us to use the same code path on all supported host platforms.
It also slightly reduces hot reload times on Linux from ~750ms to ~690ms for the unchanged flutter_gallery app and significantly reduces hot reload times on Windows from almost 1.5s to just slightly slower than on Linux.
This change will also allow us to retire `sky_snapshot` completely in the future.
* Enable Hot Reload on Windows (backed by gen_snapshot)
\o/
Two caveats:
* Hot Reload on Windows is slower than on other platforms because gen_snapshot is slower then sky_snapshot
* We currently cannot hot reload projects with spaces in the path
* enable tests
* Add a check in case the flutter directory in .packages no longer exists. Clean up and prompt user
* Update documentation to use flutter packages get for end-users instead of flutter update-packages.
* Merge missing sdk error with the multiple sdk error. They're really the same thing.
* Use flutterPath in both checks.
* Change file_system’s copy folder to copy director which takes into account the file system
* Test support files
* Add test and split into 2 messages again.
* Move tests to run in memory file system's copy. Tested with dev/bots/test.sh
- [x] Introduce DependencyChecker which can determine if any dependencies have been modified.
- [x] Move the DartDependencyBuilder into a separate file.
- [x] Add unit tests for DartDependencyBuilder.
- [x] Add unit tets for DependencyChecker
Part of #7014
