### Elasticsearch Version

8.0

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

win10

### Problem Description

I am using GCP plugin with Elasticsearch 8.0 and it seems that the settings that are specified in the documentation [here](https://www.elastic.co/guide/en/elasticsearch/reference/8.0/repository-gcs.html) are not available to use in Elasticsearch. I have further gone into investigation to investigate GCS repository plugin and below are my observations:
The settings are declared in GoogleCloudStorageClientSettings.java class [here](https://github.com/elastic/elasticsearch/blob/690bac5dc375b5a1e8f6b3b091d38ee6cdeb0b05/modules/repository-gcs/src/main/java/org/elasticsearch/repositories/gcs/GoogleCloudStorageClientSettings.java#L101) but they are not loaded in the implementation getSettings() method [here](https://github.com/elastic/elasticsearch/blob/690bac5dc375b5a1e8f6b3b091d38ee6cdeb0b05/modules/repository-gcs/src/main/java/org/elasticsearch/repositories/gcs/GoogleCloudStoragePlugin.java#L66).
Due to this elasticsearch.bat is throwing error and exiting instead of starting Elasticsearch.

### Steps to Reproduce

1. Specify the below settings in elasticsearch.yml:
gcs.client.default:
  proxy.host: "abc.com"
  proxy.port: 80
  proxy.type: "http"
2. Start elasticsearch.bat and this will generate **java.lang.IllegalArgumentException: unknown setting [gcs.client.default.proxy.host] please check that any required plugins are installed, or check the breaking changes documentation for removed settings** followed by exiting the bat script.

### Logs (if relevant)

@KarenSumner @liladler Could you please help prioritize of fixing this bug?
<img width="947" alt="elastic_bug" src="https://user-images.githubusercontent.com/100778274/156373380-203706a9-ad1d-423d-a51f-4c40189f6c92.PNG">
 
modules/repository-gcs/src/main/java/org/elasticsearch/repositories/gcs/GoogleCloudStoragePlugin.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */
package org.elasticsearch.repositories.gcs;
import org.elasticsearch.cluster.service.ClusterService;
import org.elasticsearch.common.settings.Setting;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.util.BigArrays;
import org.elasticsearch.env.Environment;
import org.elasticsearch.indices.recovery.RecoverySettings;
import org.elasticsearch.plugins.Plugin;
import org.elasticsearch.plugins.ReloadablePlugin;
import org.elasticsearch.plugins.RepositoryPlugin;
import org.elasticsearch.repositories.Repository;
import org.elasticsearch.xcontent.NamedXContentRegistry;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
public class GoogleCloudStoragePlugin extends Plugin implements RepositoryPlugin, ReloadablePlugin {