Initialize variable lists, generate object IDs, fix variable debug dump

[dmcilvaney]

These fixes allow the Authvars TA to run enough for basic testing to start.

• In memory variable lists are now initialized properly
• On clean RPMB TEE_StartPersistentObjectEnumerator() will return TEE_ERROR_ITEM_NOT_FOUND, handle this.
• Even though we don't need to keep track of the unique object IDs used to create persistent objects, OP-TEE requires they be unique. Use a truncated SHA256 hash of (GUID + Variable Name) as the object ID when creating a new variable. This ID is picked back up when enumerating the persistent objects during initialization (although we don't currently need it again).
• AuthVarDumpVarList() updated to work again, also prints volatile variables as well.

Note: The Authvar TA is currently not tracking newly created variables correctly and returns TEE_ERROR_ACCESS_CONFLICT because it attempts to create a new persistent object but the SHA256 hash always produce the same object ID for the same GUID + name.

[DMattoon]

These issues are addressed in an upcoming update (this afternoon).