Show hint type in spoiler log

[fenhl]

This adds a field hint_type to GossipRecords, which serves two purposes:

• The hint type is now explicitly listed in the spoiler log, which should be helpful for external tools parsing the gossip_stones section of a spoiler log, e.g. the simulator mode of TOoTR.
• Plando authors can now specify the hint type to place on a specific gossip stone as an alternative to directly specifying the text. This behaves differently compared to setting priority stones in the hint distribution: the plando'd hint doesn't count for the distro's fixed hint counts, and attempting to plando a hint type that can't be generated (which currently includes the hardcoded hint types Trial, Always, Dual Always, and Entrance Always) raises an exception rather than falling back to the next hint type.