Allow for conftest.py in sub directories.

Ensure async test methods work in test classes.

Add a "random" flag to randomize the test order (defaults to False).

Terminal output tidy. Non-blocking Pyodide print in main thread.

Add running_in_worker flag to output, flush print in Pyodide.

Ensure test results are always JSON serializable.

Add duration, platform and version information to test results data s…

…tructure.

Ensure results are JSON serialisable. Update test suite and README to…

… reflect this.

Added output of Python interpreter details at the start of the test d…

…etails.

Add test class detection, update test suite to exercise test class de…

…tection, refine docs, black formatted.