WorkItem List doesn't support multiple search params anymore

How to reproduce

1. Enable work_items_project_issues_list
2. Go to a project or group work item page
3. Add two search params to the URL, e.g.

http://gdk.test:3000/my-project/-/issues?search=a&search=b

The problem

Before work_items_project_issues_list we concated the search params together with an empty space inbetween, so the request was made: search: "a b".

Now, we try to send an array search: ["a", "b"] to the GraphQL query. This is conflicting though with the type we expect.

Error

getWorkItemsFullEE responds with an error because use an array for search instead of a String that is expected.

{
    "errors": [
        {
            "message": "Variable $search of type String was provided invalid value",
            "locations": [
                {
                    "line": 1,
                    "column": 114
                }
            ],
            "extensions": {
                "value": [
                    "a",
                    "b"
                ],
                "problems": [
                    {
                        "path": [],
                        "explanation": "Could not coerce value [\"a\",\"b\"] to String"
                    }
                ]
            }
        }
    ]
}