Implement storage of Elliptic Curve keys (EVP_PKEY_EC) in pkcs11_store_key()

[NSavatier]

Currently, storage of EC keys (EVP_PKEY_EC) is not supported in pkcs11_store_key(). This prevents from using PKCS11_store_private_key() (defined in libp11.h) to store this type of keys.

This proposition of implementation reuses the parse_ec_pkey() function from OpenSC's pkcs11-tool (see : https://github.com/OpenSC/OpenSC/blob/master/src/tools/pkcs11-tool.c#L4103 ) to add support for storage of EC keys.

For information, we've tested this implementation manually with openssl 3.0.13 on an NXP S32G-VNP-RDB2 card.