Start generating storage format test cases. This commit introduces two test
data files: test_suite_psa_crypto_storage_format.v0.data for reading keys in
storage format version 0 (the current version at this time), and
test_suite_psa_crypto_storage_format.current.data for saving keys in the
current format (version 0 at this time).
This commit kicks off the test case generation with test cases to exercise
the encoding of usage flags. Subsequent commits will cover other aspects of
keys.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>