### 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
final String clientName = randomBoolean() ? "default" : randomAlphaOfLength(5).toLowerCase(Locale.ROOT);
        randomClient(clientName, settings, secureSettings, deprecationWarnings);
        secureSettings.setFile(
            CREDENTIALS_FILE_SETTING.getConcreteSettingForNamespace(clientName).getKey(),
            "invalid".getBytes(StandardCharsets.UTF_8)
        );
        assertThat(
            expectThrows(
                IllegalArgumentException.class,
                () -> loadCredential(settings.setSecureSettings(secureSettings).build(), clientName)
            ).getMessage(),
            equalTo("failed to load GCS client credentials from [gcs.client." + clientName + ".credentials_file]")
        );
    }
    public void testProjectIdDefaultsToCredentials() throws Exception {
        final String clientName = randomAlphaOfLength(5);
        final Tuple<ServiceAccountCredentials, byte[]> credentials = randomCredential(clientName);
        final ServiceAccountCredentials credential = credentials.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_SETTING.getDefault(Settings.EMPTY),
            PROXY_HOST_SETTING.getDefault(Settings.EMPTY),
            PROXY_PORT_SETTING.getDefault(Settings.EMPTY)
        );