Add storage format checks to the interface checker

Expand abi_check.py to look for backward incompatibilities not only in
the interface exposed to application code (and to some extent driver
code), but also to the interface exposed via the storage format, which
is relevant when upgrading Mbed TLS on a device with a PSA keystore.

Strictly speaking, the storage format checks look for regressions in
the automatically generated storage format test data. Incompatible
changes that are not covered by the generated tests will also not be
covered by the interface checker.

A known defect in this commit is that the --brief output is not brief
for storage format checks.

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

tests/scripts/generate_psa_tests.py

@@ -725,6 +725,8 @@ class TestGenerator:
         filename = self.filename_for(basename)
         test_case.write_data_file(filename, test_cases)
 
+    # Note that targets whose name containns 'test_format' have their content
+    # validated by `abi_check.py`.
     TARGETS = {
         'test_suite_psa_crypto_generate_key.generated':
         lambda info: KeyGenerate(info).test_cases_for_key_generation(),