### 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/GoogleCloudStorageServiceTests.java
public void testClientInitializer() throws Exception {
        final String clientName = randomAlphaOfLength(randomIntBetween(1, 10)).toLowerCase(Locale.ROOT);
        final TimeValue connectTimeValue = TimeValue.timeValueNanos(randomIntBetween(0, 2000000));
        final TimeValue readTimeValue = TimeValue.timeValueNanos(randomIntBetween(0, 2000000));
        final String applicationName = randomAlphaOfLength(randomIntBetween(1, 10)).toLowerCase(Locale.ROOT);
        final String endpoint = randomFrom("http://", "https://")
            + randomFrom("www.elastic.co", "www.googleapis.com", "localhost/api", "google.com/oauth")
            + ":"
            + randomIntBetween(1, 65535);
        final String projectIdName = randomAlphaOfLength(randomIntBetween(1, 10)).toLowerCase(Locale.ROOT);
        final Settings settings = Settings.builder()
            .put(
                GoogleCloudStorageClientSettings.CONNECT_TIMEOUT_SETTING.getConcreteSettingForNamespace(clientName).getKey(),
                connectTimeValue.getStringRep()
            )
            .put(
                GoogleCloudStorageClientSettings.READ_TIMEOUT_SETTING.getConcreteSettingForNamespace(clientName).getKey(),
                readTimeValue.getStringRep()
            )
            .put(
                GoogleCloudStorageClientSettings.APPLICATION_NAME_SETTING.getConcreteSettingForNamespace(clientName).getKey(),
                applicationName