Logs all debug messages produced by GL and EGL.
This is helpful for debugging when the application does not register a
debug callback.

Validation errors produce log messages with level INFO, and internal
errors produce log messages with level WARN.

Bug: angleproject:3505
Change-Id: I269055aec49e1d77edeedb482fa6873c8f79f853
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1645817
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>