PowerShell cmdlet generation fails if a parameter is named Pipeline

[fzkhan]

Before filling a bug

• have you checked the faq for known issues.
• have you checked existing issues

Describe the bug

Please provide as much information as you can. This would be:
- OpenAPI files having the issues
- Autorest command used

When I have a parameter named pipeline in the OpenAPI spec, trying to build PowerShell cmdlets fails with this error:

error CS0102: The type 'SetResource_Put' already contains a definition for 'Pipeline'

To reproduce, here is a minimal OpenAPI spec:

{
  "swagger": "2.0",
  "info": {
    "title": "Example Client",
    "description": "Example service client",
    "version": "2.0"
  },
  "host": "localhost:3456",
  "schemes": ["http"],
  "consumes": ["application/json"],
  "produces": ["application/json"],
  "paths": {
    "/examples": {
      "put": {
        "operationId": "putResource",
        "description": "Put a resource onto our servers",
        "parameters": [
          {
            "name": "pipeline",
            "in": "body",
            "description": "Parameter names Pipeline",
            "schema": {
              "$ref": "#/definitions/Resource"
            },
            "required": true
          }
        ],
        "responses": {
          "200": {
            "description": "Received correct resource",
            "schema": {
              "type": "string"
            }
          }
        }
      }
    }
  },
  "definitions": {
    "Error": {
      "type": "object",
      "properties": {
        "status": {
          "type": "integer",
          "format": "int32"
        },
        "message": {
          "type": "string"
        }
      }
    },
    "Resource": {
      "type": "object",
      "properties": {}
    }
  }
}

Sample README file:

input-file: ./example.json
powershell: true
output-folder: Output/generated
clear-output-folder: true

PS commands:

autorest .\README.md
Set-Location .\Output\generated
./build-module.ps1

This fails with the above mentioned error. The reason seems to be naming conflicts with the internal pipeline the generated code is using:

        /// <summary>
        /// The instance of the <see cref="Sample.API.Runtime.HttpPipeline" /> that the remote call will use.
        /// </summary>
        public Sample.API.Runtime.HttpPipeline Pipeline { get; set; }

        /// <summary>Anything</summary>
        [global::System.Management.Automation.Parameter(Mandatory = true, HelpMessage = "Anything", ValueFromPipeline = true)]
        [Sample.API.Runtime.Info(
        Required = true,
        ReadOnly = false,
        Description = @"Anything",
        SerializedName = @"pipeline",
        PossibleTypes = new [] { typeof(Sample.API.Models.IAny) })]
        [global::Sample.API.Category(global::Sample.API.ParameterCategory.Body)]
        public Sample.API.Models.IAny Pipeline { get => this._pipeline; set => this._pipeline = value; }

Expected behavior
If we rename the parameter to anything other than pipeline, the module builds just fine.

Additional context
We have an ARM resource named pipeline and we would like to preserve the naming to maintain UX consistency.

Attached the erroring generated file for reference. (Sorry, GitHub does not allow .cs files, so renamed to .txt)
SetResource_Put.txt