Refactor Database fetch_results method

[kalombos]

В AsyncDatabase не должно быть метода fetch_results, логика должна быть перенесена в соответствующие Query-классы: ModelCompoundSelectQuery, RawQuery. Кстати, нужно проверить, есть ли на них тесты, насколько помню тестов на ModelCompoundSelectQuery не было.

There should not be a fetch_results method in AsyncDatabase. The logic should be transferred to the corresponding Query classes: ModelCompoundSelectQuery, RawQuery. By the way, you need to check if there are tests for them; as far as I remember, there were no tests for ModelCompoundSelectQuery.

#237 #236

[rudyryk]

Manager extracted to compatibility module in PR #232

Seems like AsyncDatabase.fetch_results might be safely removed, it actually never gets called in tests, check #233