This reverts commit 5fd259be.

This adds a smoke test for every single API example. It also fixes 17 tests that had bugs in them, or were otherwise broken, and even fixes one actual bug in the framework, and one limitation in the framework.

The bug in the framework is that NetworkImage's _loadAsync method had await response.drain<List<int>>();, but if the response is null, it will throw a cryptic exception saying that Null can't be assigned to List<int>. The fix was just to use await response.drain<void>(); instead.

The limitation is that RelativePositionedTransition takes an Animation<Rect> rect parameter, and if you want to use a RectTween with it, the value emitted there is Rect?, and one of the examples was just casting from Animation<Rect> to Animation<Rect?>, which is invalid, so I modified RelativePositionedTransition to take a Rect? and just use Rect.zero if the rect is null.

* Add missing parameters to DecorationImage

* tune docs

* fix test

Fixes test/painting/image_stream_test.dart of #85160

The problem: The timeDilation was changed to 2.0 but not restored. The changed timeDilation carried on to following tests which messed up some of them when using test ordering seed 456.

The Fix: Restore timeDilation to 1.0 at the end of test.

This reverts commit 32c2e2ba.

* Randomize tests, exclude tests that fail with randomization.

* Disable some more tool tests

This reverts commit d056500b.

This reverts commit 31de052e.

This reverts commit e2490f29.

This reverts commit b5f9612c because it is taking about 40% longer to run the tests, which is causing timeouts.

This turns on order shuffling for all tests that don't fail with it on, marking those tests that do fail with a tag so that they will be run without shuffling on.

To determine which tests fail with it on, I ran all the tests 100 times with different random shuffle seeds, and then also ran it with the date seeds from today until the end of July, and tagged all of the test suites (files) that fail, with a seed that caused them to fail.

* Fix single frame image is decoded even cached

* Add MultiFrameImageStreamCompleter decode test for one frame image