OpenCL/Vulkan: Implement compile and link routines Enables the following OpenCL APIs for the Vulkan Backend: clCompileProgram clLinkProgram Bug: angleproject:8571 Change-Id: Ide7d2911922347055051537c9c70b83be4e24575 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5341375 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Austin Annestrand <a.annestrand@samsung.com> Reviewed-by: Geoff Lang <geofflang@chromium.org>