Give WebSocketContainer on the client side a lifecycle

Currently there is no way for the implementation to know when the developer has finished using each instance of the WebSocketContainer. If the developer uses ContainerProvider.getWebSocketContainer() to obtain many instances, this is difficult to manage for the implementation.

Consider adding a lifecycle so the implementation can clean up.

Start by reviewing WebSocketContainer and ContainerProvider.getWebSocketContainer() to understand how client-side instances are obtained and used. Define the lifecycle and cleanup behavior the implementation should observe, then identify the API and compatibility implications. Done means the lifecycle is specified clearly and validated with tests for obtaining, finishing, and cleaning up container instances.

Written by the indexing model from the issue text.