Drupal\Core\Database\Query\Condition driver must now be overridden by all database drivers

Drupal 9 now requires all database drivers to contain an implementation of the Drupal\Core\Database\Query\Condition class. This will allow the entire Database API to access custom methods if they must be overridden. For databases which do not require customized condition methods, a stubbed class file is all that is needed. This change aligns the Condition class with the requirements for the Delete, Merge, Select, Transaction, Truncate, Update, and Upsert classes.