Move ShaderVariable utility function from utilities.cpp ShaderVars.cpp. Fixes an implied dependency cycle between translator and angle_common. This will also allow us to be more strict about declaring dependencies on GLSLANG headers. Tested by building and running angle_unit_tests on Linux. Bug: angleproject:4672 Change-Id: I331230d2cf179ccea140ee7a0d5a3c8768c58cb1 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2222682 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>