Overriding title in `getModelSchemaRef` causes duplication in OpenAPI schema

まだ誰も着手していません。

## 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.

packages/openapi-v3/src/controller-spec.ts の、参照されているパラメーター列挙の周辺から始め、requestBody スキーマと推論されたモデルコンストラクターが OpenAPI コンポーネントに入る経路を追ってください。title のオーバーライドケースを再現し、その後、スキーマがすでに参照されているリクエストボディが未使用の重複スキーマを生成しないことを確認してください。

索引モデルが issue の本文から書いたものです。