some shaderLab bug

[zhuxudong]

Describe the bug

• [ ] can't call v2f function outside vertex|frag in ShaderLab

      VertexShader = vert;
      FragmentShader = frag;

      v2f vert_internal(a2v v, float FUR_OFFSET){
         v2f o;
         o.v_uv = v.TEXCOORD_0;
         o.v_normal = v.NORMAL;
         return o;
      }

      void frag_internal(v2f i, float FUR_OFFSET){
        gl_FragColor = vec4(1,0,0,1);
      }
      
      v2f vert(a2v v) {
        return vert_internal(v, 0.05);
      }

      void frag(v2f i) {
        frag_internal(i, 0.05);
      }

• [ ] can't inherit global renderState
• [x] can't write uniform outside Multi pass