Implement interruptible ECC Export Public Key (Headers)

[paul-elliott-arm]

Stage 1 of implementing interruptible ECC export public key.

This should involve implementing the documentation and function headers for psa_export_public_key_iop_setup(), psa_export_public_key_iop_complete() and psa_export_public_key_iop_abort() as well as base definition of structs psa_export_public_key_iop_t and psa_export_public_key_iop_s and their corresponding initialisers. Generated files will neeed regenerating to cover these new functions and basic implementations will have to be included, as generated tests will end up calling these tests. These implementations should simply return PSA_ERROR_NOT_IMPLEMENTED.

PSA documentation for interruptible functions here ARM-software/psa-api#199

Function prototypes for reference:

psa_status_t psa_export_public_key_iop_abort(psa_export_public_key_iop_t * operation);
psa_status_t psa_export_public_key_iop_complete(psa_export_public_key_iop_t * operation,
                                                uint8_t * data,
                                                size_t data_size,
                                                size_t * data_length);
uint32_t psa_export_public_key_iop_get_num_ops(psa_export_public_key_iop_t * operation);
psa_export_public_key_iop_t psa_export_public_key_iop_init(void);
psa_status_t psa_export_public_key_iop_setup(psa_export_public_key_iop_t * operation,
                                             psa_key_id_t key);

[yanesca]

Completed by #9778.