* Clean up some flutter_tools tests
* Remove arbitrary retry that happens even for fundamental errors, and generally clean up _DevFSHttpWriter.
* Update dependencies (requires fixes; see next commit)
* Fixes for new dependencies.
The current API was broken in that you registered multiple
callbacks at once, but when you removed listeners, only the
primary listener was used to determine what was removed.
This led to unintuitive cases where the caller could get
unexpected behavior.
This updates the API to add and remove listeners using
a newly introduced [ImageStreamListener] object, a value
object that has references to the individual callbacks
that may fire.
flutter/flutter#24722flutter/flutter#32374flutter/flutter#32935
