@realm/react tests sometimes hanging on CI

[tomduncalf]

The @realm/react tests are sometimes hanging on CI. When run locally, you get this error:

A worker process has failed to exit gracefully and has been force exited. This is likely caused by tests leaking due to improper teardown. Try running with --detectOpenHandles to find leaks. Active timers can also cause this, ensure that .unref() was called on them.

But running with --detectOpenHandles does not seem to help – the tests either pass, or hang forever.

Workaround is to run with --forceExit but it would be good to work out what causes this.

Screenshots from example run on CI:

(this will hang at this point until the build times out)