psa_get_and_lock_transparent_key_slot_with_policy() function

Get a key slot containing a transparent key and lock it. A transparent key is a key for which the key material is directly available, as opposed to a key in a secure element and/or to be used by a secure element. This is a temporary function that may be used instead of psa_get_and_lock_key_slot_with_policy() when there is no opaque key support for a cryptographic operation. On success, the returned key slot has been registered for reading. It is the responsibility of the caller to then unregister once they have finished reading the contents of the slot. The caller unregisters by calling psa_unregister_read() or psa_unregister_read_under_mutex(). psa_unregister_read() must be called if and only if the caller already holds the global key slot mutex (when mutexes are enabled). psa_unregister_read_under_mutex() encapsulates psa_unregister_read() with mutex lock and unlock operations.