FrameCapture: Move MEC of program binaries to a helper This creates a new function called GenerateLinkedProgram that will facilitate capture support of glProgramBinary. Note this also moves one line out of the GenerateLinkedProgram path because it modifies state. The new function needs to be run against const state mid-capture in the next CL. Test: Fortnite MEC Bug: b/180418810 Bug: angleproject:5658 Change-Id: I4e3a7f3ff8d31b07bb0ebc220858a66e91e24933 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3105389 Commit-Queue: Cody Northrop <cnorthrop@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com>