* fix some formatting issues

* address review comments

* fix indent

* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test

This machinery is useful for arbitrary boxes (e.g., with FittedBox).

Fixes #6463

This patch improves test coverage for a number of files that had low
coverage. This patch also fixes a few minor bugs found by these tests.

Also, add FractionalOffset.inscribe.