Overriding title in `getModelSchemaRef` causes duplication in OpenAPI schema

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## Steps to reproduce

Define a controller with `getModelSchemaRef(SomeModel, {title: 'TitleOverride'})`.

Controller definition

```typescript
export class UserController {
@post('/users', {
security: OPERATION_SECURITY_SPEC,
responses: {
'200': {
description: 'User',
content: {
'application/json': {
schema: {
'x-ts-type': User,
},
},
},
},
},
})
async create(
@requestBody({
content: {
'application/json': {
schema: getModelSchemaRef(NewUserRequest, {
title: 'NewUser',
}),
},
},
})
newUserRequest: NewUserRequest,
): Promise {
// implementation
}
}
```

## Current Behavior

The controller above emits schema definitions for both `NewUserRequest` and `NewUser`. While `NewUserRequest` is not referenced anywhere else in the schema.

## Expected Behavior

Only `NewUser` is present in OpenAPI schema.

## Additional information

`@loopback/repository-json-schema@2.4.2`
`@loopback/openapi-v3@3.4.1`

I presume `NewUserRequest` is generated from `getModelSchemaRef` as it should while `NewUser` comes from parsing `paramTypes` where it causes a cache miss due to overridden `title`.

A probable fix could exclude a parameter corresponding to `requestBody` from enumeration here

https://github.com/strongloop/loopback-next/blob/7f8d8356946dc236dd4daecbfae12e0a0662cf1c/packages/openapi-v3/src/controller-spec.ts#L329

## Acceptance Criteria

- [ ] Don't generate unused schema for parameter decorated with `@requestBody`

A solution I can think of is:
https://github.com/strongloop/loopback-next/blob/7f8d8356946dc236dd4daecbfae12e0a0662cf1c/packages/openapi-v3/src/controller-spec.ts#L329

should search through the content objects in the request body spec, if all contents' schemas exist in reference, then skip generating the one inferred from model ctor.

Inizia in packages/openapi-v3/src/controller-spec.ts, intorno all’enumerazione dei parametri indicata, e segui come gli schemi di requestBody e i costruttori dei modelli inferiti entrano nei componenti OpenAPI. Riproduci il caso di override di title, quindi verifica che un corpo della richiesta il cui schema è già referenziato non generi uno schema duplicato inutilizzato.

Scritto dal modello di indicizzazione a partire dal testo della issue.