Adding 3 options to allow users to control performance and quality of shadows.

Front Face Culling (Simple and Variance): Enables front face culling during the shadow pass to decrease artifacts, but does not always render thin objects (such as planes).

Soft Shadows (Variance): Enables the blurring step for variance shadow maps. Enabled matches the old behavior.

Low Precision (Variance): Renders shadow maps using an RG16 image format instead of an RG32F format. This can improve performance for large resolutions, but can introduce some artifacts (the bias option can usually correct these artifacts).