FrameCapture: Add ReplayWriter helper class. This centralizes all of the replay file I/O into a single point. Each function is stored separately in this class. Right now there's some small file format changes: - the namespaces for the capture label are gone. these had no functional impact now that each trace was a separate module. - the header is cleaned up into private and public functions. this cleans up a few things like defining non-existent functions. - inline variables are tracked through the replay. they are now global instead of anonymous, and string sets get reused instead of duplicated between frames. There should be no functional changes with the naming of the trace files or the trace behaviour. This change sets the stage for the ReplayWriter buffering multiple frames into a single cpp file on disk, which can potentially reduce the number of object files in the compilation by a great deal. It could also be extended to work with buffered I/O so we don't block and hitch when we're writing large trace files. Bug: angleproject:5133 Change-Id: Ib96685e1202ac8101a4b828fa79642236af2120a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3311940 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>