WIP: Tests for GL_EXT_gpu_shader4 without GL 3.0
This ports various GLSL 130 tests to use GL_EXT_gpu_shader4 without requiring GL 3.0. Some of it is duplicating tests to have GL_EXT_gpu_shader4 variants. Some is making tests work both ways. Currently marked WIP because I'm not convinced we have full GL_EXT_gpu_shader4 coverage yet. However, having a MR which everyone can push to makes collaboration easier.