This PR addresses two issues related to creating repair orders from return transfers:

### The First issue:
Steps to reproduce the issue:
- Activate `is_repairable` option on any picking type, let's say "Receipts"
- Create a delivery order with any product(s).
- Validate it.
- Return it.
- Validate the generated receipt transfer.
- From the generated receipt, click on "Repair" button on the top.
- Fill the required fields of the repair order and confirm it.
- Add any part (`stock.move`) to the repair order.

Expected behavior:
- The new `stock.move` is created and the availability is determined based on quantities in stock.

Current behavior:
- The created `stock.move` is not only attached to the repair order, but is also attached to the related return transfer.
- Since the return transfer may be done, no stock move lines are assigned to the newly linked move, which affects the availability making it unavailable.
- This availablity status also affects the repair order making it unable to reserve any quantity for its parts.

The issue is because clicking on "Repair" button from `stock.picking` form, adds `default_picking_id` to the context variable to be used on the `repair.order` form. When creating stock moves from the repair order form, the `default_picking_id` key in the context is propagated and used to link the new move to a picking, hence, leading to this undesired behavior.

### The Second Issue:
Steps to reproduce the issue:
- Create a delivery order.
- Validate it.
- Return it.
- Without navigating to another page, validate the generated receipt order.
- Click on "Repair" button.
- Select any product on the RO form.

Expected behavior:
- Form is saved and the repair order is created.

Current behavior:
- Validation error shows: "A mandatory field is not set", `parts_location_id`.

The issue is caused by `default_picking_type_id` key that exists in the context variable when a return order is created from another transfer. This variable propagates to the creation of the repair order and is used instead of the correct picking type which is "Repairs" in that case.

Task-3877625

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Forward-Port-Of: odoo/odoo#164385
Forward-Port-Of: odoo/odoo#162452