* This is better than testing by platform/platform version, because we can check
specifically for extensions and avoid running a test we know will fail because
extensions aren't supported.
* We also pick the output pixel in the CBuffer_Zoo tests to ensure the API
agrees with our interpretation of the data.
* Follow-up commit will tidy D3D cbuffer code that needs it.
* Built entirely independently of the main renderdoc build (for now).
* Contains python scripts & framework for running tests on a renderdoc build,
which will be run nightly.