generator: Fix broken union type anyOf selection since Redfish 2024.1

[Nitorac]

Hi, I propose a minor fix that helps fixing the issue for union types in the OpenAPI spec after Redfish 2024.1.

In Redfish 2023.1 Resource.yaml, the Location resource looks like this:

    Resource_Location:
      anyOf:
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_1_15.yaml#/components/schemas/Resource_v1_1_15_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_2_14.yaml#/components/schemas/Resource_v1_2_14_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_3_13.yaml#/components/schemas/Resource_v1_3_13_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_4_12.yaml#/components/schemas/Resource_v1_4_12_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_5_11.yaml#/components/schemas/Resource_v1_5_11_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_6_11.yaml#/components/schemas/Resource_v1_6_11_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_7_10.yaml#/components/schemas/Resource_v1_7_10_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_8_10.yaml#/components/schemas/Resource_v1_8_10_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_9_8.yaml#/components/schemas/Resource_v1_9_8_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_10_5.yaml#/components/schemas/Resource_v1_10_5_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_11_4.yaml#/components/schemas/Resource_v1_11_4_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_12_3.yaml#/components/schemas/Resource_v1_12_3_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_13_2.yaml#/components/schemas/Resource_v1_13_2_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_14_1.yaml#/components/schemas/Resource_v1_14_1_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_15_0.yaml#/components/schemas/Resource_v1_15_0_Location
      - $ref: http://redfish.dmtf.org/schemas/v1/Resource.v1_16_0.yaml#/components/schemas/Resource_v1_16_0_Location
      description: The location of a resource.
      x-longDescription: This type shall describe the location of a resource.

So the redfish-generator works as expected on this structure.

But since Redfish 2024.1, it looks like this:

    Resource_Location:
      $ref: ./Resource.v1_19_1.yaml#/components/schemas/Resource_v1_19_1_Location
      description: The location of a resource.
      x-longDescription: This type shall describe the location of a resource.

This leads to the UnionContextFactory to ignore this kind of resources that fallback into a simple pub struct Location;.

As a patch, I propose to still support getAnyOf if any works, but add the support for the simple .get$ref() on these resources.

I'm still pretty new with the Redfish specification so I am open for any improvements on this code !