Convert the PSA crypto cryptography tests to the new handle API

Switch from the direct use of slot numbers to handles allocated by
psa_allocate_key.

This commit does not affect persistent key tests except for the one
test function in test_suite_psa_crypto that uses persistent keys
(persistent_key_load_key_from_storage).

The general principle for each function is:
* Change `psa_key_slot_t slot` to `psa_key_handle_t handle`.
* Call psa_allocate_key() before setting the policy of the slot,
  or before creating key material in functions that don't set a policy.
* Some PSA_ERROR_EMPTY_SLOT errors become PSA_ERROR_INVALID_HANDLE
  because there is now a distinction between not having a valid
  handle, and having a valid handle to a slot that doesn't contain key
  material.
* In tests that use symmetric keys, calculate the max_bits parameters
  of psa_allocate_key() from the key data size. In tests where the key
  may be asymmetric, call an auxiliary macro KEY_BITS_FROM_DATA which
  returns an overapproximation. There's no good way to find a good
  value for max_bits with the API, I think the API should be tweaked.

tests/suites/test_suite_psa_crypto.data

@@ -29,17 +29,15 @@ PSA import to non empty key slot
 depends_on:MBEDTLS_AES_C
 import_key_nonempty_slot
 
-PSA export empty key slot
-export_invalid_slot:1:PSA_ERROR_EMPTY_SLOT
+PSA export invalid handle (0)
+export_invalid_handle:0:PSA_ERROR_INVALID_ARGUMENT
 
-PSA export out of range key slot - lower bound
-export_invalid_slot:0:PSA_ERROR_INVALID_ARGUMENT
+PSA export invalid handle (smallest plausible handle)
+# EMPTY_SLOT is temporary, because this valie is treated as a numbered slot, not as a handle
+export_invalid_handle:1:PSA_ERROR_EMPTY_SLOT
 
-PSA export out of range key slot - upper bound
-# Hard-code the upper bound of slots that are directly accessible because the
-# API does not expose this value. This is temporary: directly-accessible
-# slots are about to be removed.
-export_invalid_slot:32767:PSA_ERROR_INVALID_ARGUMENT
+PSA export invalid handle (largest plausible handle)
+export_invalid_handle:-1:PSA_ERROR_INVALID_HANDLE
 
 PSA export a slot where there was some activity but no key material creation
 export_with_no_key_activity