Capture/Replay: Move stub implementation to new file. This lets the MSVC parser work better with FrameCapture.cpp. Bug: angleproject:3611 Change-Id: I249106dce81a7965684caf1a835f0472b34e8963 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1804878 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tobin Ehlis <tobine@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>