Manual roll Flutter Engine from 6745955bb49e to 6cefbe183546 (6 revisions) (#144996)

Manual roll requested by zra@google.com

https://github.com/flutter/engine/compare/6745955bb49e...6cefbe183546

2024-03-11 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Move emscripten out of the buildroot into the flutter repo. (#51299)" (flutter/engine#51330)
2024-03-11 skia-flutter-autoroll@skia.org Roll Skia from ff1eb5af6ce4 to 6f10903e2d28 (3 revisions) (flutter/engine#51326)
2024-03-11 matanlurey@users.noreply.github.com Conditionally run `golden_tests_harvester` for `run_impeller_golden_tests`. (flutter/engine#51325)
2024-03-11 skia-flutter-autoroll@skia.org Roll Dart SDK from c3bd630e89bb to 09a1a1ede1c4 (1 revision) (flutter/engine#51324)
2024-03-11 jacksongardner@google.com Move emscripten out of the buildroot into the flutter repo. (flutter/engine#51299)
2024-03-11 skia-flutter-autoroll@skia.org Roll Skia from f8d5ecc7841d to ff1eb5af6ce4 (2 revisions) (flutter/engine#51322)

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

-6745955bb49e4e894a47cb48a19ffba504c69613
+6cefbe183546461bdcdf7633a4cd5021cce2f210