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/Services/EmbedService.cs

@@ -16,10 +16,10 @@ namespace PluralKit.Bot {
     public class EmbedService
     {
         private IDataStore _data;
-        private DbConnectionFactory _db;
+        private Database _db;
         private DiscordShardedClient _client;
 
-        public EmbedService(DiscordShardedClient client, IDataStore data, DbConnectionFactory db)
+        public EmbedService(DiscordShardedClient client, IDataStore data, Database db)
         {
             _client = client;
             _data = data;