Failures on [vm/ffi] Example with deeply-immutable Finalizable and dart_api_dl

[bkonyi]

There are new test failures on [vm/ffi] Example with deeply-immutable Finalizable and dart_api_dl.

The tests

ffi/deeply_immutable_c_api_finalizer_test Timeout (expected Pass)

are failing on configurations

vm-win-debug-x64

[dcharkes]

Log: https://dart-ci.appspot.com/log/vm-win-debug-x64/vm-win-debug-x64/3530/ffi/deeply_immutable_c_api_finalizer_test

stdout:
Instance of 'MyFinalizable'
Pointer: address=0x1d72074e060
123

The test output is being printed, but the main function doesn't seem to exit.

I'm suspecting the issue is allocating with package:ffi with CoTaskMemAlloc and then calling free.
We should allocate on Windows with the calloc that's linked in ffi_test_functions instead of looking up CoTaskMemAlloc.

CL: https://dart-review.googlesource.com/c/sdk/+/356801