Capture/Replay: Isolate trace export definitions. This small fix to the export header means we no longer include the "restricted_traces_autogen.h" in each and every trace file. That means when we change/add/remove a trace we no longer need to recompile each and every trace. Speeds up iteration time when working with the traces. Also fixes inconsistent path generation on Windows. Bug: angleproject:5133 Change-Id: I357d65477a683455d01379379e2e98431af2ed55 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3110749 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>