### Elasticsearch Version

8.x (any version where we have added support for proxies with a GCS repo)

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

N/A

### Problem Description

When configuring a GCS repository with HTTP proxy settings ([doc](https://www.elastic.co/guide/en/elasticsearch/reference/8.0/repository-gcs.html#repository-gcs-client)), we do not pass along the proxy settings to other `HttpTransportOptions` instances that we create. This can lead to timeout errors when the GCS Client tries to get a token, with the following error message:
```
Error getting access token for service account: Connect timed out, iss: ...
```

The workaround is to set the HTTP proxy settings on the JVM level rather than when defining the GCS repository, using `java.net.useSystemProxies` or `http.proxyHost`/`http.proxyPort`.

### Steps to Reproduce

[Setting up a GCS repository](https://www.elastic.co/guide/en/elasticsearch/reference/8.0/repository-gcs.html) with HTTP proxy settings (while every other non-proxied GCP call is blocked) could lead to this issue.

### Logs (if relevant)

_No response_
modules/repository-gcs/src/test/java/org/elasticsearch/repositories/gcs/GoogleCloudStorageClientSettingsTests.java
"http://localhost:8443",
                "https://www.googleapis.com/oauth/token"
            );
            settings.put(ENDPOINT_SETTING.getConcreteSettingForNamespace(clientName).getKey(), endpoint);
        } else {
            endpoint = ENDPOINT_SETTING.getDefault(Settings.EMPTY);
        }
        String projectId;
        if (randomBoolean()) {
            projectId = randomAlphaOfLength(5);
            settings.put(PROJECT_ID_SETTING.getConcreteSettingForNamespace(clientName).getKey(), projectId);
        } else {
            projectId = PROJECT_ID_SETTING.getDefault(Settings.EMPTY);
        }
        TimeValue connectTimeout;
        if (randomBoolean()) {
            connectTimeout = randomTimeout();
            settings.put(CONNECT_TIMEOUT_SETTING.getConcreteSettingForNamespace(clientName).getKey(), connectTimeout.getStringRep());
        } else {
            connectTimeout = CONNECT_TIMEOUT_SETTING.getDefault(Settings.EMPTY);
        }
        TimeValue readTimeout;
        if (randomBoolean()) {
            readTimeout = randomTimeout();
            settings.put(READ_TIMEOUT_SETTING.getConcreteSettingForNamespace(clientName).getKey(), readTimeout.getStringRep());
        } else {
            readTimeout = READ_TIMEOUT_SETTING.getDefault(Settings.EMPTY);
        }
        String applicationName;
        if (randomBoolean()) {