Invalid shader is generated when refraction is enabled without metalness

[mvaligursky]

Refraction (both cubemap and dynamic) can only be used with metalness. Otherwise we get shader compilation errors. Ideally this should work as well, or at least force useMetalness perhaps.

Note that this issues exist and can be reproduce both in engine V2 and V1.

Repros:

1. engine example Material-refraction, just comment out 'material.useMetalness = true;'
2. Editor. Create a new material, open Refraction section, and set Refraction value to non-zero.

related to #7513