Elastic Cloud Enterprise (ECE) shares snapshot repositories across multiple deployments. As a result, the `base_path` is generated by ECE, and the `base_path` setting is not allowed. This PR adds a note to the S3, Azure, and GCS snapshot repository docs.
* Add support for HTTP Proxies for the GCS repository
The change adds 3 new client properties for the GCS repository:
* gcs.client.default.proxy.type
* gcs.client.default.proxy.host
* gcs.client.default.proxy.port
They allow to configure a [java.net.Proxy](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/net/Proxy.html)
for the GCS SDK to use when communicating with the GCS API.
Resolves#82444
Closes#81652.
Convert the `repository-azure`, `repository-gcs` and `repository-s3`
plugins into modules, so that they are always included in the
Elasticsearch distribution. Also change plugin installation, removal
and syncing so that attempting to add or remove these plugins still
succeeds but is now a no-op.
debadair
James Rodewig
Dan Roscigno
Artem Prigoda
Rory Hunter