Using Association::find() in Association::attachTo()

This allows us to use defined custom finders even for joinable associations.
Removed unit tests that were hard to follow and were fragile, the code
they covered is also covered by a few integration tests.

src/ORM/Association.php

@@ -433,7 +433,6 @@ public function attachTo(Query $query, array $options = []) {
 			'type' => empty($options['matching']) ? $this->joinType() : 'INNER',
 			'table' => $target->table()
 		];
-		$options['conditions'] = array_merge($this->conditions(), $options['conditions']);
 
 		if (!empty($options['foreignKey'])) {
 			$joinCondition = $this->_joinCondition($options);
@@ -442,7 +441,7 @@ public function attachTo(Query $query, array $options = []) {
 			}
 		}
 
-		$dummy = $target->query()->eagerLoaded(true);
+		$dummy = $this->find()->eagerLoaded(true);
 		if (!empty($options['queryBuilder'])) {
 			$dummy = $options['queryBuilder']($dummy);
 			if (!($dummy instanceof Query)) {