[Dashboard navigation] By-reference Links panels add input attributes to Dashboard saved objects

[nickpeihl]

Bug affects the navigation-embeddable feature branch only. Not present in main.

When adding a by-reference Links panel to a dashboard, the panelsJSON for the dashboard still contains the entire embeddable input as well as the panelRefName.

For example, here is a parsed snippet of a panelsJSON from a dashboard saved object containing a by-reference links panel. Notice that the attributes are included as well as the panelRefName.

{
    "version": "8.10.0",
    "type": "navigation_embeddable",
    "gridData": {
        "x": 0,
        "y": 0,
        "w": 24,
        "h": 15,
        "i": "491de79e-9a6f-4efd-b25f-874190a48781"
    },
    "panelIndex": "491de79e-9a6f-4efd-b25f-874190a48781",
    "embeddableConfig": {
        "attributes": {
            "title": "linksss",
            "description": "",
            "links": [
                {
                    "type": "dashboardLink",
                    "id": "55fcffb6-ca69-42ed-9318-e57ab3890586",
                    "destination": "722b74f0-b882-11e8-a6d9-e546fe2bba5f",
                    "order": 0
                },
                {
                    "type": "dashboardLink",
                    "id": "cb01500b-f8fc-404d-8770-2a02562e8537",
                    "destination": "edf84fe0-e1a0-11e7-b6d5-4dc382ef7f5b",
                    "order": 1
                }
            ],
            "layout": "vertical"
        },
        "disabledActions": [
            null,
            "OPEN_FLYOUT_ADD_DRILLDOWN"
        ],
        "enhancements": {}
    },
    "panelRefName": "panel_491de79e-9a6f-4efd-b25f-874190a48781"
}

This likely went unnoticed in #160896.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[nickpeihl]

Fixed by #164887