Roll engine 876c4c339064..8b5a50c0df76 (4 commits) (#31237)

https://github.com/flutter/engine/compare/876c4c339064...8b5a50c0df76

git log 876c4c339064ed321f37fba61422194d84cbfdb7..8b5a50c0df768743dd9858cceb92d1d1de44c35e --no-merges --oneline
8b5a50c0d Test saving compilation traces. (flutter/engine#8618)
7d3caf895 Avoid leaking the VM in runtime_unittests and update failing tests. (flutter/engine#8626)
91b71070f Revert "Add a unit test for PhysicalShapeLayer (#8616)" (flutter/engine#8627)
8b667b017 Add a unit test for PhysicalShapeLayer (flutter/engine#8616)

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bin/internal/engine.version

-876c4c339064ed321f37fba61422194d84cbfdb7
+8b5a50c0df768743dd9858cceb92d1d1de44c35e