Roll Flutter Engine from 8a859c5b3a2d to 03ebd6460b83 (2 revisions) (#144746)

https://github.com/flutter/engine/compare/8a859c5b3a2d...03ebd6460b83

2024-03-07 jonahwilliams@google.com [Impeller] add a per-frame trace event for heap usage on Vulkan. (flutter/engine#51246)
2024-03-07 chris@bracken.jp Move Abseil from src to flutter third_party dir (flutter/engine#51245)

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.

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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

-8a859c5b3a2dffc4e23eb78312eac79efbfa808a
+03ebd6460b83346b8aa55f4fb79f185e8ccb1593