Suricata

Avoid future #5408 by passing the Flow to AppLayerParserGetTx and similar API calls.

Something like:

void *AppLayerParserGetTx(const Flow *f, AppProto alproto, void *alstate, uint64_t tx_id);

Perhaps we can also take alstate from the Flow, but this needs a good review to see how the functions are called.

alproto is often a constant, so we should probably keep it that way.