LibQuery: Add option to NOT process embedded IDs.

Request from depsgraph department, which does basically consider those
embedded IDs as any other data-block (unlike any BKE ID management code).

source/blender/blenkernel/BKE_lib_query.h

@@ -116,6 +116,8 @@ enum {
   IDWALK_READONLY = (1 << 0),
   IDWALK_RECURSE = (1 << 1),    /* Also implies IDWALK_READONLY. */
   IDWALK_INCLUDE_UI = (1 << 2), /* Include UI pointers (from WM and screens editors). */
+  /** Do not process ID pointers inside embedded IDs. Needed by depsgraph processing e.g. */
+  IDWALK_IGNORE_EMBEDDED_ID = (1 << 3),
 
   IDWALK_NO_INDIRECT_PROXY_DATA_USAGE = (1 << 8), /* Ugly special case :(((( */
 };