Roll engine 8ed5da8..ef99738 (6 commits) (flutter#36790)

flutter/engine@8ed5da8...ef99738

git log 8ed5da8..ef99738 --no-merges --oneline
ef99738 Added a DartExecutor API for querying # of pending channel callbacks (flutter/engine#10021)
a0ec528 Embedding testing app (flutter/engine#10007)
2bf1506 Disable DartLifecycleTest::ShuttingDownTheVMShutsDownAllIsolates in runtime_unittests. (flutter/engine#10064)
8edd257 Roll fuchsia/sdk/core/linux-amd64 from M5an7VPM8DiCcNcKe6J0CkAtLk8X9oMeJUqGOrZATIsC to XqtWTBni4xpYCTr7gqU7rFTuXNY1TZ_zOqBJrZM8c_kC (flutter/engine#10061)
e32bdf5 Roll src/third_party/skia 00c680d2bb7c..e11dfd3da4d7 (18 commits) (flutter/engine#10062)
6603dbd Update .cirrus.yml (flutter/engine#10056)

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bin/internal/engine.version

@@ -1 +1 @@
-8ed5da8b655db6dd47718b03d1d909e098f7864a
+ef99738bafc08861412655ec0a84e966c98c633a