Manual roll Flutter Engine from 6cefbe183546 to 67713071563e (5 revisions) (#145002)

Manual roll requested by zra@google.com

flutter/engine@6cefbe1...6771307

2024-03-11 ditman@gmail.com [web] Split initialization of the _flutter namespace and loader object. (flutter/engine#51294)
2024-03-11 skia-flutter-autoroll@skia.org Roll Dart SDK from 09a1a1ede1c4 to 7a2c94fd0a26 (1 revision) (flutter/engine#51338)
2024-03-11 skia-flutter-autoroll@skia.org Roll Skia from 6f10903e2d28 to 32f1cb50734a (5 revisions) (flutter/engine#51331)
2024-03-11 34871572+gmackall@users.noreply.github.com Make scenario app have translucent splash screen so it doesn't affect screenshot colors (flutter/engine#51329)
2024-03-11 zanderso@users.noreply.github.com [gn] Change sdk_rewriter() template to use depfiles (flutter/engine#51314)

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

Author: engine-flutter-autoroll

bin/internal/engine.version

@@ -1 +1 @@
-6cefbe183546461bdcdf7633a4cd5021cce2f210
+67713071563ecda1becc9d9ee635b66aa60a1a4a