Add messages for framebuffer completeness errors. This also creates a common code path for all framebuffer completeness errors (FramebufferStatus::Incomplete) which helps for adding a debug breakpoint. Bug: angleproject:5949 Change-Id: Ib102dbf86e020777e56c6dc6b78dda8ebdba2127 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2888110 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>