Roll Flutter Engine from 5bbac1a5c576 to 31bbe61dfa0d (3 revisions) (#144724)

https://github.com/flutter/engine/compare/5bbac1a5c576...31bbe61dfa0d

2024-03-06 flar@google.com add new builder benchmark with a global saveLayer (flutter/engine#51236)
2024-03-06 bdero@google.com [Flutter GPU] Move method tests to flutter_tester. (flutter/engine#51223)
2024-03-06 zanderso@users.noreply.github.com Disable flaky linux desktop test (flutter/engine#51231)

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

-5bbac1a5c5762e93c130c08123e0e856efc73996
+31bbe61dfa0d19cb883cb7e3ab58c04127b94d4c