Security
   * Unlike previously documented, enabling MBEDTLS_PSA_HMAC_DRBG_MD_TYPE does
     not cause the PSA subsystem to use HMAC_DRBG: it uses HMAC_DRBG only when
     MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG and MBEDTLS_CTR_DRBG_C are disabled.
