Capture/Replay: Encapsulate cpp replay.

This moves the cpp replay logic out of the FrameCapture class into pure
c helper functions. This is a bit cleaner and could help us eventually
move to writing out the cpp replay on a worker thread.

Bug: angleproject:3611
Change-Id: I6a96c1ef1595a6203d44c1d4d9d793205701dd24
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1804879
Commit-Queue: Jamie Madill <[email protected]>
Reviewed-by: Cody Northrop <[email protected]>
Reviewed-by: Tobin Ehlis <[email protected]>

Author: null77