Vulkan: Prepare for variable-stage pipelines Compute (single-stage pipeline) is upcoming, but this change prepares GlslangWrapper to handle any number of stages (mostly). Additionally, this change binds each resource to each stage based on whether it's active, so that we don't hit the per-stage limit of resources by binding every resource to every stage. Bug: angleproject:3633 Bug: angleproject:3562 Change-Id: Ifebf691482846e0371c6e314f514226a4cfee258 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1689330 Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>