Config resolver substitutes config instead of merging.

Steps:

1. On Ibexa Commerce 4.6 install connector-unsplash and set up Unsplash as described in doc.
2. Create Image Asset CT.
3. Create IA content item.
4. Examine available buttons.

Actual result: "Select from DAM" button is not present.
Expected result: It is possible to select assets from Unsplash.

Remarks: The problem is with this element of configuration - "content.dam: [ unsplash ]". On 4.6 system.<scope>.content is present in config/packages in both ibexa.yaml and ibexa_admin_ui.yaml (on 4.5 only in ibexa.yaml). On 4.6 when "content.dam" is added only to ibexa.yaml it gets replaced by "content" section from ibexa_admin_ui.yaml.