feat(multiset): hook up startsession and unlocks routines

[wescopeland]

This should be the final back-end PR required to facilitate emulator support for multiset.

This PR makes an adjustment to getUserAchievementUnlocksForGame(), which is used by both the startsession and unlocks routines. The function now returns unlock metadata for all sets attached to the given game ID.

Additionally, both startsession and unlocks will attempt to pass the "parent" game ID into getUserAchievementUnlocksForGame(). For example, given the game ID 1, they will pass in 1. Given the game ID 29895, they will pass in 1.

---

GET dorequest.php?u=WCopeland&t=redacted&r=startsession&m=09dadb5071eb35050067a32462e39c5f&g=29895

{
	"Success": true,
	"HardcoreUnlocks": [
		{
			"ID": 2,
			"When": 1693271855
		},
		{
			"ID": 9,
			"When": 1693271901
		},
		{
			"ID": 16,
			"When": 1693272238
		},
		{
			"ID": 18,
			"When": 1693273061
		},
		{
			"ID": 436757, <------- subset unlock
			"When": 1737400430
		}
	],
	"Unlocks": [
		{
			"ID": 101000001,
			"When": 1737404678
		}
	],
	"ServerNow": 1737404678
}

---

GET /dorequest.php?u=WCopeland&t=redacted&r=unlocks&m=09dadb5071eb35050067a32462e39c5f&g=29895

{
	"Success": true,
	"UserUnlocks": [
		2,
		9,
		16,
		18,
		436757, <--------- subset unlock
		101000001
	],
	"GameID": 29895,
	"HardcoreMode": false
}

[Jamiras]

Didn't do thorough testing, but verified a subset unlock comes back when starting a session for a core set.