Flaky test on aarch64_repeated and nightly_win_rep: test_multi_nested_message_introspection

[clalancette]

It looks like there is a rare flake on the nightly aarch64 repeated tests.

In particular, the test that fails is rosidl_typesupport_introspection_tests.MultiNestedMessageIntrospectionTest/0.CanWriteTypeErasedMessage. There are two relatively recent instances of it:

• https://ci.ros2.org/view/nightly/job/nightly_linux-aarch64_repeated/2277/
• https://ci.ros2.org/view/nightly/job/nightly_linux-aarch64_repeated/2297/

There is more detail in the links above, but when it fails, it looks something like:

/home/jenkins-agent/workspace/nightly_linux-aarch64_repeated/ws/src/ros2/rosidl/rosidl_typesupport_introspection_tests/test/test_multi_nested_message_introspection.cpp:212
Expected equality of these values:
  item_reference
    Which is: 736-byte object <E0-D1 06-B7 FF-FF 00-00 E0-BC ED-DB FF-FF 00-00 20-EC D2-FF AA-AA 00-00 20-EC D2-FF AA-AA 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 ... 01-00 00-00 00-00 00-00 20-73 D3-FF AA-AA 00-00 09-00 00-00 00-00 00-00 0A-00 00-00 00-00 00-00 40-73 D3-FF AA-AA 00-00 09-00 00-00 00-00 00-00 0A-00 00-00 00-00 00-00 00-00 00-00 AA-AA 00-00>
  message.array_of_arrays[i]
    Which is: 736-byte object <E0-D1 06-B7 FF-FF 00-00 E0-D1 06-B7 FF-FF 00-00 20-EC D2-FF AA-AA 00-00 20-EC D2-FF AA-AA 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00 ... 01-00 00-00 00-00 00-00 30-07 D3-FF AA-AA 00-00 09-00 00-00 00-00 00-00 0A-00 00-00 00-00 00-00 10-07 D3-FF AA-AA 00-00 09-00 00-00 00-00 00-00 0A-00 00-00 00-00 00-00 00-00 00-00 00-00 00-00>

[Yadunund]

Reported on nightly_win_rep: https://ci.ros2.org/view/nightly/job/nightly_win_rep/2955/testReport/(root)/projectroot/test_multi_nested_message_introspection/