Add storage tests for lifetimes

Test keys with various persistence levels, enumerated from the
metadata tests.

For read-only keys, do not attempt to create or destroy the key
through the API, only to read a key that has been injected into
storage directly through filesystem access.

Do not test keys with a non-default location, since they require a
driver and we do not yet have a dependency mechanism to require the
presence of a driver for a specific location value.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

scripts/mbedtls_dev/psa_storage.py

@@ -164,6 +164,10 @@ class Key:
         """
         return self.bytes().hex()
 
+    def location_value(self) -> int:
+        """The numerical value of the location encoded in the key's lifetime."""
+        return self.lifetime.value() >> 8
+
 
 class TestKey(unittest.TestCase):
     # pylint: disable=line-too-long