Search & Filter: Call GET /orders-storage/orders

Overview:
Currently the GET /orders/composite-orders endpoint calls the mod-orders-storage endpoint GET /orders-storage/purchase-orders which queries the purchase order table directly. Now that GET /orders-storage/orders is implemented to query a view combining several tables, it should be used instead...

Current:
GET /orders/composite-orders ==> GET /orders-storage/purchase-orders

Desired:
GET /orders/composite-orders ==> GET /orders-storage/orders

Acceptance Criteria:

• The behavior has been changed as described above
• Unit tests (mocks) are updated as needed
• API Tests are updated to exercise searching for purchase orders via criteria in poLines, etc. - part of MODORDERS-219