Roll Flutter Engine from d13479968b8f to 820645dbcc69 (3 revisions) (#141152)

https://github.com/flutter/engine/compare/d13479968b8f...820645dbcc69

2024-01-09 skia-flutter-autoroll@skia.org Roll Skia from e3af4a11007d to 06404ed554e7 (1 revision) (flutter/engine#49614)
2024-01-09 magder@google.com Roll buildroot to pick up iOS 12 (flutter/engine#49542)
2024-01-09 skia-flutter-autoroll@skia.org Roll Skia from f4626a2e3293 to e3af4a11007d (1 revision) (flutter/engine#49613)

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 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

-d13479968b8f2c1ac358a12b5d89dd76f7f0aa88
+820645dbcc6951da0a142fc12683f01aa95651d0