Capture/Replay: Serialize trace metadata to a JSON file. This will allow us to remove more code auto-generation for the trace tests. The trace info now can be loaded directly from JSON instead of from the autogenerated information. Bug: angleproject:5133 Change-Id: I04e22b9279b19282df274bc8defcd363d0449111 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3140218 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com>