### 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
assertEquals(credential.getProjectId(), googleCloudStorageClientSettings.getProjectId());
    }
    public void testLoadsProxySettings() throws Exception {
        final String clientName = randomAlphaOfLength(5);
        final ServiceAccountCredentials credential = randomCredential(clientName).v1();
        final GoogleCloudStorageClientSettings googleCloudStorageClientSettings = new GoogleCloudStorageClientSettings(
            credential,
            ENDPOINT_SETTING.getDefault(Settings.EMPTY),
            PROJECT_ID_SETTING.getDefault(Settings.EMPTY),
            CONNECT_TIMEOUT_SETTING.getDefault(Settings.EMPTY),
            READ_TIMEOUT_SETTING.getDefault(Settings.EMPTY),
            APPLICATION_NAME_SETTING.getDefault(Settings.EMPTY),
            new URI(""),
            Proxy.Type.HTTP,
            "192.168.15.1",
            8080
        );
        assertEquals(
            new Proxy(Proxy.Type.HTTP, new InetSocketAddress(InetAddress.getByName("192.168.15.1"), 8080)),
            googleCloudStorageClientSettings.getProxy()
        );
    }
    
    private Tuple<Map<String, GoogleCloudStorageClientSettings>, Settings> randomClients(
        final int nbClients,
        final List<Setting<?>> deprecationWarnings
    ) throws Exception {
        final Map<String, GoogleCloudStorageClientSettings> expectedClients = new HashMap<>();
        final Settings.Builder settings = Settings.builder();
        final MockSecureSettings secureSettings = new MockSecureSettings();