Make SQL Expression & Query classes abstract

[mvorisek]

Specific driver class is needed to determine correct SQL template and identifier escape character.

Instead of:

new Expression(['connection' => $connection]);
new Query(['connection' => $connection]);

always use

$connection->expr()
$connection->dsql();

Also removing new DBAL 3.4+ support temporary, as many changes are needed like for https://github.com/doctrine/dbal/pull/5513/files#r945271960.