tools/importer-rest-api-specs: parsing the dfe types into regular Object Definition Types

[tombuildsstuff]

Rather than using the type field to define the type for a given field within the Swagger API Definition like other services, Data Factory uses a meaningless value for type (typically object) which gets overridden by an x-ms-format value that references some dfe specific types - which refer to these C# types hand-defined within the C# AutoRest generator (HT @ziyeqf)

Since importer-rest-api-specs doesn't know to check for this field, this means that the following field within the API Definition:

        "headers": {
          "type": "object",
          "x-ms-format": "dfe-key-value-pairs",
          "additionalProperties": {
            "type": "string",
            "x-ms-format": "dfe-string"
          }
        },

Gets parsed out as an Object rather than a Dictionary[String]. There's a bunch of these DFE types and these can be found within the DataFactory API definitions, but these will align with the list defined in the C# generator above.

As such, we need to update importer-rest-api-specs to parse the Data Factory specific types into a regular Object Definition Types so that hashicorp/go-azure-sdk can output the correct types.

See also Azure/azure-rest-api-specs#28380

[tombuildsstuff]

We might also need to do some additional duck-typing here to find out the values for this field, since this is being masked in the API definition with the way Expressions are implemented: Azure/azure-rest-api-specs#28538 / #4076

[tombuildsstuff]

Split List[Reference] out into #4238