Adds system mouse cursor to the Android engine.

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/fuchsia-mac-sdk-flutter-engine
Please CC liyuqian@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

* runs ios unit tests, if the simulator is already booted.

* address reviewer comments

* changing comments for the Safari desktop tests

* addressing reviewer comments. removing the timeout.

* change mobile browsers ver name for safari.dart

* removing then calback on browser exit, only leaving the exception callback

These are removed in destructors.

This updates the references to `third_party/dart/sdk` to
`third_party/dart/sdk_nnbd`

Fixes: https://github.com/flutter/flutter/issues/58431

* Fix nineslice assertion

* implement SkPath.computeMetrics

This format is preferred on some hardware. Also explicitly
specify color space when creating the skia surface.
Co-authored-by: NDavid Reveman <reveman@google.com>

See https://github.com/KhronosGroup/Vulkan-Samples/blob/master/samples/performance/layout_transitions/layout_transitions_tutorial.md#transaction-elimination-on-mali-gpus
for an explanation of why transitioning the layout hurts performance
on Mali drivers.
Co-authored-by: NDavid Reveman <reveman@google.com>

Choose a child more likely to remain stable from frame to frame as the target to cache in the OpacityLayer.

This reverts commit 0622b051.

Unblocks: flutter/flutter#57135

Part of https://github.com/flutter/flutter/issues/38478