Optimize setting texture uniforms

[ScanMountGoat]

This will greatly improve rendering performance. Many of the validation checks are redundant. For a generic material, the checks should only be performed once per shader.

[ScanMountGoat]

This is partially fixed by e58a466b8d3a299097ab81f9bea76d0356cb69dd. Skipping redundant uniform validation will also improve performance, but will be harder to implement correctly.