Rename db.system to db.system.name per OTel semantic conventions v1.40+

The semantic conventions renamed db.system to db.system.name. The
well-known value for Firebird is 'firebirdsql', not 'firebird'.
Updated in both FbActivitySource (spans) and FbConnection (metrics).

Author: fdcastel

src/FirebirdSql.Data.FirebirdClient/FirebirdClient/FbConnection.cs

@@ -194,7 +194,7 @@ public override string ConnectionString
 				_connectionString = value;
 
 				MetricsConnectionAttributes = [
-					new("db.system", "firebird"),
+					new("db.system.name", "firebirdsql"),
 					new("db.namespace", _options.Database),
 					new("server.address", $"{_options.DataSource}:{_options.Port}")
 				];

src/FirebirdSql.Data.FirebirdClient/Trace/FbActivitySource.cs

@@ -44,7 +44,7 @@ internal static Activity CommandStart(FbCommand command)
 			if (activity is not { IsAllDataRequested: true })
 				return activity;
 
-			activity.SetTag("db.system", "firebird");
+			activity.SetTag("db.system.name", "firebirdsql");
 
 			if (dbCollectionName != null)
 			{