Add a template to generate a complete list of tests for C/C++, and use it to generate the list of binaries to run tests for.

Instead of third party simplejson module, to save a dependency.

By default don't re-run tests that have already run successfully, to
reduce latency between making a change and seeing if it fixed the last
thing that you were trying to fix.

MSAN, TSAN, ASAN need to see all the code. Valgrind, MSAN want -DPURIFY.

 -) Fixing long line length.
 -) Changed the logic of the exit message.

  -) Adding a new command line flag to be able to see which tests are passing.
  -) Adding more status when the tool is idle in forever mode.
  -) Adding a last status when the tool is finished so to avoid leaving the console in a weird state.
  -) Adding a status message in the forever mode if the previous run failed.
  -) Swapped the message and its explanation, so you don't have to scroll up to see which test failed.
  -) Fixed a race condition in the watch_dir.py code if a file is deleted during the loop.

Also allow maxjobs to be tweaked based upon which configs are being run,
to prevent memory starvation.

Also allow maxjobs to be tweaked based upon which configs are being run,
to prevent memory starvation.

If not running in forever mode, and a test fails, fail run_tests.py
also.

If running in forever mode and make fails, wait for the next run.

If not running in forever mode, and a test fails, fail run_tests.py
also.

If running in forever mode and make fails, wait for the next run.

This is a tool for collecting coverage reports from our tests and
combining them with the open-source tool 'lcov'.

At least until they stabilize some.