Several more database-y refactors

- DbConnectionFactory renamed to "Database", will now be the primary entry point for DB stuff
- Created IPKConnection interface mostly containing async extensions to IDbConnection, use this going forward
- Reworked the Connection/Command wrappers (that have performance/logging extensions)
- Probably more stuff that I forgot???

PluralKit.Bot/Commands/SystemEdit.cs

@@ -18,10 +18,10 @@ namespace PluralKit.Bot
     public class SystemEdit
     {
         private IDataStore _data;
-        private DbConnectionFactory _db;
+        private Database _db;
         private EmbedService _embeds;
 
-        public SystemEdit(IDataStore data, EmbedService embeds, DbConnectionFactory db)
+        public SystemEdit(IDataStore data, EmbedService embeds, Database db)
         {
             _data = data;
             _embeds = embeds;