[BUG][csharp] oneOf with arrays is generating duplicated 'GetList'

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating a model with a oneOf of arrays, the generated model contains two GetList which result in the following error when building:

error CS0111: Type 'OneOfArrayRequest' already defines a member called 'GetList' with the same parameter types

openapi-generator version

7.12.0 (latest master)

OpenAPI declaration file content or url

openapi: 3.0.1
info:
  title: Oneof array test
  version: 1.0.0
servers:
- url: /
paths:
  /one-of-array:
    post:
      description: Oneof array test
      operationId: oneOfArray
      requestBody:
        content:
          application/json:
            schema:
              oneOf:
              - items:
                  type: string
                type: array
              - items:
                  $ref: '#/components/schemas/TestObject'
                type: array
      responses:
        "204":
          description: Successful operation
components:
  schemas:
    TestObject:
      properties:
        name:
          type: string
      type: object

Generation Details

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -i ./oneOfArray.yaml -g csharp -o test

Steps to reproduce

Generate using the command above and try to build the generated code

Start by running the provided OpenAPI declaration with the shown openapi-generator CLI command and inspect the generated C# model for duplicate GetList methods. Trace how the oneOf array schemas are rendered, then confirm the generated project builds without CS0111 and cover the case with a regression test if the existing test structure supports it.