message: improve depth test usage and tracking
  We now disable the depth test entirely when possible. this should save
  a few gl calls.
diff: @@ -681,11 +681,16 @@ void OpenGLDriver::setRasterStateSlow(RasterState rs) noexcept {
  }
  // depth test
  + if (rs.depthFunc == RasterState::DepthFunc::A && !rs.depthWrite) {
  + disable(GL_DEPTH_TEST);
  + } else {
  + enable(GL_DEPTH_TEST);
  depthFunc(getDepthFunc(rs.depthFunc));
  + depthMask(GLboolean(rs.depthWrite));
  + }
  // write masks
  colorMask(GLboolean(rs.colorWrite));
  - depthMask(GLboolean(rs.depthWrite));
  // AA
  if (rs.alphaToCoverage) {
  