feat: Generate ArrayMap

[matheusandre1]

Mention:
quarkiverse/quarkus-openapi-generator#1352 and quarkiverse/quarkus-openapi-generator#1611 (review)

Bug in OpenApi2JaxRs - additionalProperties as an array does not generate Map<String, List<...>>

Description:

• In OpenApi2JaxRs, the schema below is not being correctly converted to a map type:

ApiLists:
  type: object
  additionalProperties:
    type: array
    items:
      $ref: '#/components/schemas/ApiList'
  x-codegen-inline: true

Current Behavior

• The generator does not produce the expected bean.

• The map is not generated as Map<String, List>.

• There seems to be a lack of support for additionalProperties whose value is an array of references.
  Expected Behavior

• The schema should generate the equivalent representation:
  Map<String, List>

• If the generator needs to create an auxiliary type, it should be something functionally equivalent that preserves String → List.

Why it's a bug
This pattern is valid in OpenAPI and is common for representing objects whose values ​​are lists of models.
The generator should treat additionalProperties with type: array + items: $ref as a map of lists, not as an unsupported case.

Implementation Requirements

• Add support for recognizing additionalProperties with type: array.
• Ensure that references in items are resolved correctly.
• Generate the correct map type in the final code.

[matheusandre1]

@mcruzdev Check if I'm forgetting anything.