Remove ProgramExecutable's "isCompute" property. This consolidates the lists of uniforms, ssbos, etc into one. Requires a few checks to change from graphics shader stages into all shaders. Bug: angleproject:6596 Change-Id: Ic8f6bfc4fa295c3bea9f5f1ded11e8fbca1c3164 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3233361 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>