- Update a few validation tests to not use render count.
- Update scripts to use `const`/`let` instead of `var`.
- Update validation script to handle some errors better and clean up dead code.
- Add unhandled exception handler to Playground app so that validation test will report correct errors and exit correctly.
- Change core graphics device implemenation to update bgfx state right before requesting screenshots. This will ensure the screenshot is the right size if the resolution has changed.
- Fix TestUtils:WritePNG to return an error when the byte length is an unexpected size instead of silently failing.
- Change TestUtils::SetTtitle to update the HWND title on a background thread to avoid dead lock with the main thread.

…into update-bjs

…xture ownership