Sqlite: Improve SqliteStatement

There are now only value and values methods. value returns an optional
and values are returning a vector. The result value count has now be
specified instead of the result value list.

Change-Id: I17a0741d5e838b4bf4b9486825c870ada1722584
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/libs/sqlite/sqlitedatabasebackend.cpp

@@ -420,7 +420,7 @@ Type DatabaseBackend::toValue(Utils::SmallStringView sqlStatement)
 
     statement.next();
 
-    return statement.value<Type>(0);
+    return statement.fetchValue<Type>(0);
 }
 
 } // namespace Sqlite