Merge the two identical definitions of TEST_USES_KEY_ID and
mbedtls_test_psa_purge_key_storage from
test_suite_psa_crypto_slot_management.function and
test_suite_psa_crypto_se_driver_hal.function into a single copy in
common test code so that it can be used in all test suites.
No semantic change.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>