shell and runtime tests are failing with async dispatcher issues #57124
Description
shell_unittests are failing:
Full log: https://chromium-swarm.appspot.com/task?id=4c277fa7baf27b10
[ RUN ] ShellTest.VSyncTargetTime
[INFO:test_timeout_listener.cc(76)] Test timeout of 30 seconds per test case will be enforced.
ASSERT FAILED at (../../fuchsia/sdk/linux/pkg/fidl_cpp/internal/message_reader.cc:106): dispatcher_ != nullptr
either |dispatcher| must be non-null, or |async_get_default_dispatcher| must be configured to return a non-null value
runtime_unittests are failing:
Full log: https://chromium-swarm.appspot.com/task?id=4c276e87fcb2d910
[ RUN ] DartIsolateTest.CanSaveCompilationTrace
[INFO:test_timeout_listener.cc(76)] Test timeout of 30 seconds per test case will be enforced.
[ERROR:flutter/runtime/dart_isolate.cc(465)] Could not resolve main entrypoint function.
[ERROR:flutter/testing/dart_isolate_runner.cc(144)] Could not run the method "thisShouldNotExist" in the isolate.
[ERROR:flutter/runtime/dart_isolate_unittests.cc(159)] Hello from Dart!
ASSERT FAILED at (../../fuchsia/sdk/linux/pkg/inspect_service_cpp/service.cc:106): dispatcher