feat: aggregate cluster statistics and send to influx with scheduled tasks worker

PluralKit.Core/CoreConfig.cs

@@ -6,6 +6,7 @@ public class CoreConfig
 {
     public string Database { get; set; }
     public string RedisAddr { get; set; }
+    public bool UseRedisMetrics { get; set; } = false;
     public string SentryUrl { get; set; }
     public string InfluxUrl { get; set; }
     public string InfluxDb { get; set; }

PluralKit.Core/CoreMetrics.cs

@@ -102,4 +102,12 @@ public static class CoreMetrics
         MeasurementUnit = Unit.Connections,
         Context = "Database"
     };
+}
+
+public record ClusterMetricInfo
+{
+    public int GuildCount;
+    public int ChannelCount;
+    public int DatabaseConnectionCount;
+    public int WebhookCacheSize;
 }