[cryptotest] Add parser for manual hjson ECDSA tests

[RyanTorok]

Adds a parser to incorporate the manual hjson ECDSA verify tests in /sw/device/tests/crypto/testvectors/ecdsa_p256_verify_hardcoded.hjson into the existing cryptotest framework. I verified the tests pass when applied on top of #20853 with the P-256 patch in #21115 applied.

[RyanTorok]

It would make the hjson very hard to read, because many of the values in the test vectors are stored as byte arrays, and we would have to hard-code an array of bytes.