Custom openapi parameter defined in XML is not displayed in UI

**API Platform version(s) affected**: 4.1 (and probably some older versions as well)

**Description**

I define some custom parameters with `` XML element. This custom parameter is not being displayed in the OpenAPI UI under the desired operation.

Technical problem in the json:
OpenAPI parameter should not be indexed by its name but by integer index.

Such is described in [OpenAPI spec](https://swagger.io/docs/specification/v3_0/describing-parameters/) where parameters are array of objects, not object with fields (indexed by a string).

**How to reproduce**
I define custom parameter in XML like this:
```

string

```

Then I get this OpenAPI spec (reduced):
```
"\/api\/client\/auth\/economic-subjects": {
"get": {
"operationId": "api_clientautheconomic-subjects_get",
"parameters": {

// this string index
"businessTitle": {

"name": "businessTitle",
"in": "query",
"description": "The title of the business to search for.",
"required": true,
"deprecated": false,
"allowEmptyValue": false,
"schema": {
"type": "string"
},
"style": "form",
"explode": false,
"allowReserved": false
}
},
"deprecated": false
}
}
```
but this parameter indexed by string in the resulting json do not show up in the UI.

**Possible Solution**
When I make a change in the class [`metadata/Extractor/XmlResourceExtractor.php`](https://github.com/api-platform/core/blob/main/src/Metadata/Extractor/XmlResourceExtractor.php) such as
```
foreach ($openapi->parameters->parameter as $parameter) {
$data['parameters'][(string) $parameter->attributes()->name] = new OpenApiParameter(
name: $this->phpize($parameter, 'name', 'string'),
```
into
```
foreach ($openapi->parameters->parameter as $parameter) {
$data['parameters'][] = new OpenApiParameter(
name: $this->phpize($parameter, 'name', 'string'),
```
resulting json looks like this:
```
"\/api\/client\/auth\/economic-subjects": {
"get": {
"operationId": "api_clientautheconomic-subjects_get",
"summary": "Retrieves a AresEconomicSubject resource.",
"description": "Retrieves a AresEconomicSubject resource.",
"parameters": [

// no string index
{

"name": "businessTitle",
"in": "query",
"description": "The title of the business to search for.",
"required": true,
"deprecated": false,
"allowEmptyValue": false,
"schema": {
"type": "string"
},
"style": "form",
"explode": false,
"allowReserved": false
}
],
"deprecated": false
}
},
```
and the defined parameter (and others) is showing up in the UI.