MD: X.509 hashing

[mpg]

Currently X.509 uses PSA for hashing only in some places. This task is to use it (conditionally on MBEDTLS_USE_PSA_CRYPTO) everywhere.

Provide a PSA version, using psa_hash_compute(), of all remaining calls to mbedtls_md() or mbedtls_sha1_ret(), namely:

• mbedtls_md() in x509_crt_verifycrl() in x509_crt.c
• mbedtls_md() in mbedtls_x509write_crt_der() in x509write_crt.c
• mbedtls_sha1_ret() in mbedtls_x509write_crt_set_subject_key_identifier()inx509write_crt.c`
• mbedtls_sha1_ret() in mbedtls_x509write_crt_set_authority_key_identifier()inx509write_crt.c`

Note: a helper function mbedtls_psa_translate_md() is available from mbedtls/psa_util.h.

While at it, in the following functions that already have PSA version, it currently uses the multi-part API (with psa_hash_operation_t) but can be simplified to use the single-part API psa_hash_compute():

• x509_crt_check_signature()
• mbedtls_x509write_csr_der_internal()