Move Vulkan GlslangWrapper code to a shared location. Metal backend will reuse Vulkan's GlslangWrapper code. The Metal backend will use this code to translate glsl to spirv then cross compile to Metal Shading Language using spirv-cross. So the source code of GlslangWrapper should be moved outside vulkan folder. Bug: angleproject:2634 Change-Id: I208062daf0d77756c9d32cfdab925b7dfdf83e05 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1858042 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>