prop224: Refactor rend_data_t so be able to use multiple HS version
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Break rend_data_t into something that could looks like this (or maybe without a union...):
struct rend_data_t {
uint32_t version; /* XXX: Maybe not necessary if our code flow doesn't
* require us to learn the version through that data struct. */
union {
hs_data_v2_t v2;
hs_data_v3_t v3;
} hs;
};Once we have such construction, we can use v3 with that data structure more cleanly.