This file will be used with multi-frame captures to share common code.
Common code is global state, resource maps, and a list of frame replay
functions. This should make converting a CPP replay into a functional
test quite a bit simpler. The replay files will now be something like:

angle_capture_context1.cpp
angle_capture_context1.h
angle_capture_context1_frame000.cpp
angle_capture_context1_frame001.cpp
... etc

Also adds a template for adding a capture/replay sample. Instructions
are located in samples/BUILD.gn and docs in doc/CaptureAndReplay.md.

Bug: angleproject:3611
Change-Id: I437b338fd84689d670a7d9e3e219d9334de25fd8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1869543
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>
Reviewed-by: Cody Northrop <cnorthrop@google.com>