PortableRunnerTest - consider using pytest-timeout

[damccorm]

If the proposal in https://issues.apache.org/jira/browse/BEAM-9009 is completed, pytest-timeout will be able to be used to do the same timeout via sigalrm logic as in the setup and teardown methods of this test class.

Imported from Jira BEAM-9011. Original Jira may contain additional context.
Reported by: udim.