This change adds an optional UsdUtilsProcessingFunc parameter to UsdUtilsComputeAllDe...

This change adds an optional UsdUtilsProcessingFunc parameter to UsdUtilsComputeAllDependencies.  This allows for users to inject custom logic into asset discovery.  It is important to note that in this case, modifications to asset paths and dependencies are not wrriten back to the underlying layers.  The motivation for this change was to allow for filtering of certain layers in order to match specific behavior of previous versions of this function.

(Internal change: 2312250)