Roll Flutter Engine from af1fd1724986 to 9db394dbc007 (5 revisions) (#145018)

https://github.com/flutter/engine/compare/af1fd1724986...9db394dbc007

2024-03-12 bdero@google.com [Impeller] Fix shader depth assignment & glyph atlas transform. (flutter/engine#51343)
2024-03-12 jacksongardner@google.com Reland "Move emscripten out of the buildroot into the flutter repo" (flutter/engine#51353)
2024-03-12 skia-flutter-autoroll@skia.org Roll Skia from c123cce23f20 to 6e1f7333b2c7 (1 revision) (flutter/engine#51356)
2024-03-12 skia-flutter-autoroll@skia.org Roll Skia from 32f1cb50734a to c123cce23f20 (9 revisions) (flutter/engine#51351)
2024-03-12 chris@bracken.jp Migrate perfetto to flutter/third_party (flutter/engine#51272)

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

-af1fd172498602bfa6b621f0c8c705442437228b
+9db394dbc0074610d31b857d8545a3e6362904c3