Water used newMeshShader (runtime glslc compile), which is unsupported on
Windows (compileGlslWithGlslc throws there), failing graphics.water.* tests in
the Windows CI job. Extract the water fragment to shaders/water.frag, compile
it to water_frag_spv.inc, and create the shader via newMeshShaderFromSpv so it
works on every platform. Add compile_graphics_water_shaders.py.