run test suites inside test binaries in parallel by executing the test binary multiple times

Adds a tool otest-query which will return a JSON array of test class names.

Adds the option -parallelizeSuites N to run test suites in parallel, with each task getting N suites to run.

This gives around a 4x speedup for a particularly large test binary with N=8 (which I have empirically determined to be a good number).