Roll Flutter Engine from 21f055f7d8d0 to b3af5d64d3e6 (1 revision) (#138113)

https://github.com/flutter/engine/compare/21f055f7d8d0...b3af5d64d3e6

2023-11-08 jason-simmons@users.noreply.github.com [Impeller] Create a global Vulkan instance in PlaygroundImplVK to prevent SwiftShader from being unloaded after a test completes (flutter/engine#47781)

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

To file a bug in Flutter: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

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

bin/internal/engine.version

-21f055f7d8d07f723621ff76fb973cb772ea4f1b
+b3af5d64d3e6e2110b07d71909fc432537339659