misc: small Avalonia project restructure

Moved AppLibrary, Configuration, and PlayReport namespaces to Ryujinx.Systems, add the compat list stuff in the base Ryujinx.Systems namespace.
Moved the compatibility UI stuff to the proper UI view/viewmodel folders.

src/Ryujinx/Systems/AppLibrary/ApplicationMetadata.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Text.Json.Serialization;
+
+namespace Ryujinx.Ava.Systems.AppLibrary
+{
+    public class ApplicationMetadata
+    {
+        public string Title { get; set; }
+        public bool Favorite { get; set; }
+
+        [JsonPropertyName("timespan_played")]
+        public TimeSpan TimePlayed { get; set; } = TimeSpan.Zero;
+
+        [JsonPropertyName("last_played_utc")]
+        public DateTime? LastPlayed { get; set; } = null;
+
+        [JsonPropertyName("time_played")]
+        [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+        public double TimePlayedOld { get; set; }
+
+        [JsonPropertyName("last_played")]
+        [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
+        public string LastPlayedOld { get; set; }
+
+        /// <summary>
+        /// Updates <see cref="LastPlayed"/>. Call this before launching a game.
+        /// </summary>
+        public void UpdatePreGame()
+        {
+            LastPlayed = DateTime.UtcNow;
+        }
+
+        /// <summary>
+        /// Updates <see cref="LastPlayed"/> and <see cref="TimePlayed"/>. Call this after a game ends.
+        /// </summary>
+        public void UpdatePostGame()
+        {
+            DateTime? prevLastPlayed = LastPlayed;
+            UpdatePreGame();
+
+            if (!prevLastPlayed.HasValue)
+            {
+                return;
+            }
+
+            TimeSpan diff = DateTime.UtcNow - prevLastPlayed.Value;
+            double newTotalSeconds = TimePlayed.Add(diff).TotalSeconds;
+            TimePlayed = TimeSpan.FromSeconds(Math.Round(newTotalSeconds, MidpointRounding.AwayFromZero));
+        }
+    }
+}