fix(stats): save stats on attempt and populate stats UI

[xWalfie-SMR]

this addresses issue #43

Stats.Save() was never called after updating stats in LegacyRunner.Stop(), so it only stayed in memory.
StatsPanel.Update() was empty, so the stats panel never displayed any values

[nyuwaea]

Very nice, this fix works on my end. The only issue is that Update() isn't called after launching the game, I believe setting up a Saved signal in Stats listened to by StatsPanel would work best.
Storing the Labels through _Ready() or with the Export annotation could also speed up Update() but it should be called infrequently enough where it likely doesn't matter too much.

[xWalfie-SMR]

Sure, ill work on setting it up tomorrow, Stats already has [GlobalClass] so it should be straightforward