translator: Put ShaderLang APIs in "sh" namespace. Working with glslang in Vulkan means we are static linking libANGLE with functions that have the same name as our translator APIs. We can fix this by scoping our APIs. We don't need to scope the types of the file, since they don't conflict. This will require a follow-up patch to remove the unscoped APIs once we switch over Chromium. We also scope TCompiler and some related classes to avoid multiply defined link errors with glslang. BUG=angleproject:1576 Change-Id: I729b19467d2ff7d374a82044b16dbebdf2dc8f16 Reviewed-on: https://chromium-review.googlesource.com/408337 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>